How Do Staffing Agencies Work? A Complete Guide

When I started at Kelly 24 years ago, fresh out of college and working a full-service desk, most employers thought about their workforce in simple terms: they had employees, and when they needed more help, they called an agency. That was more or less the whole picture.

That picture's not quite as clear anymore. Today, most employers will tell you their workforce is no longer just one thing. Full-time employees sit alongside independent contractors and temporary talent, which is a shift that has been building for years. The share of workers identifying as independent grew from roughly 27% in 2016 to 36% by the early 2020s, and that number has only kept climbing. Managing that complexity is a fundamentally different challenge than filling an open req. The staffing agencies that are best positioned to help look nothing like the ones from two decades ago.

This guide breaks down how staffing agencies work and how the industry has evolved from transactional vendor to workforce strategy partner.

What is a staffing agency?

A staffing agency connects employers with talent. That's the simple answer, but the mechanics of that relationship are worth understanding clearly, because they shape everything from how candidates are sourced to how costs are structured.

The basic model involves three parties: the employer, the agency, and the candidate. The employer brings a workforce need. The agency sources, screens, and presents qualified candidates. When a placement is made, the agency functions as the employer of record, handling payroll, benefits administration, and compliance while the talent performs work on the client's site or remotely.

This arrangement is known as co-employment, and while the term sometimes gives organizations pause, a good staffing partner will help you understand and manage it as a straightforward feature of the relationship.

Agencies usually generate revenue either through a markup on the hourly pay rate for temporary workers or through a placement fee for permanent hires, which is typically a percentage of the hired candidate's first-year salary. That fee structure keeps agencies genuinely invested in match quality, since a strong placement benefits everyone involved.

Staffing agencies also absorb significant employer-side responsibilities, including:

• Payroll taxes
• Workers' compensation
• Unemployment insurance
• Regulatory compliance

For organizations trying to scale quickly or manage a variable workforce, that transfer of administrative burden is often as valuable as the talent itself.

Types of staffing engagements

One of the first things I explain to any new client is that 'staffing' isn't a single thing. The engagement model matters as much as the agency you choose, and finding the right fit from the start is one of the easiest ways to get more value from the relationship.

• Temporary Staffing: This model is good for finding short-term placements for immediate capacity needs, including seasonal demand, project surges, or employee absences.
• Contract-to-hire: A candidate works on a temporary basis before both parties decide whether to convert to permanent employment.
• Direct hire and permanent placement: The agency manages full-cycle recruiting for a permanent role, charging a placement fee rather than an ongoing markup.
• Specialized and industry-specific agencies: Some firms recruit exclusively within a discipline, bringing sector-specific expertise that generalist agencies can't match. For instance, at Kelly nearly 80% of our science recruiters hold science backgrounds themselves. That domain expertise changes the quality of the match.
• Managed Service Providers (MSPs): Rather than filling individual reqs, an MSP orchestrates an organization's entire external workforce program across vendors, geographies, and disciplines.

Most organizations find their needs span more than one of these models, and often evolve over time. A partner with capabilities across all five, like Kelly Services, can adapt as those needs change, rather than forcing every situation into the same solution.

How the staffing process works

Working a full-service desk early in my career gave me a ground-level view of how much happens before a candidate ever shows up for their first day. Here's what it actually looks like from the employer's side.

1. Intake and discovery. The process starts with a conversation about what you actually need. That includes the job description, but also the context behind it. Why is this role open? What does success look like at 90 days? What have past hires in this role struggled with? A good agency asks questions that go beyond the req, because the req alone rarely tells the whole story.
2. Candidate sourcing. The agency draws on its existing talent network, active sourcing channels, and in some cases proprietary databases to identify candidates who match the role requirements. For specialized positions, this is where sector-specific expertise pays off. Knowing where to find qualified talent in a given field is a skill in itself.
3. Screening and vetting. The screening process typically includes resume review, skills assessments, interviews, reference checks, and background screening. The agency does the filtering so the employer's hiring team spends time only on candidates worth evaluating seriously.
4. Presentation and selection. The agency presents a shortlist of vetted candidates with context: resumes alongside assessments of fit, relevant experience, and anything else that helps the employer make a faster, more informed decision.
5. Placement and onboarding. Once a candidate is selected, the agency handles the offer, paperwork, and onboarding logistics. For temporary placements, this includes getting the worker on payroll and confirming worksite details. The goal is to make the start date as smooth as possible for both sides.
6. Ongoing management. The relationship doesn't end at placement. A good staffing partner stays close, checking in with both the employer and the placed worker, addressing issues early, and tracking performance over time. That ongoing contact is what allows the relationship to deepen and the agency to bring better insight to the next conversation.

How staffing agencies have evolved

Early in my career, I heard former Kelly CEO Carl Camden say something that has stuck with me ever since: "The war for talent has ended and the talent has won." At the time it felt like a bold prediction. Today it reads like an accurate description of where we have landed. Workers move from company to company, building skills and curating experiences on their own terms, and employers who didn't adapt have spent years paying for it in turnover.

Years later, the data tells the same story. The average organization's contingent workforce currently sits at around 21% of their total headcount, with respondents expecting that figure to grow to 26% within the next decade. For most large employers, the blended workforce is already a reality. The harder problem is building the infrastructure to manage it well.

From staffing vendor to workforce solutions partner

That shift in workforce composition is what makes the distinction between a 'staffing vendor' and a 'workforce solutions partner' worth taking seriously, even if it sounds like semantics on the surface.

When a client calls with a hiring need, my first instinct is to understand what's driving that need before I start pulling resumes. Is this role perpetually open because of attrition? Is the attrition a compensation issue, a management issue, or something about how the role is structured? Are there multiple vendors filling similar roles across the organization that could be consolidated into a single program?

Those are workforce strategy questions, and answering them is what a true solutions partner is supposed to do. Seventy-five percent of companies now have statement-of-work consultants integrated into their external workforce programs, which reflects how far the conversation has moved beyond simple temp placements.

What the modern staffing toolkit looks like

Kelly founded this industry 80 years ago. That history gives us a depth of pattern recognition that's hard to replicate. When we sit across from a client facing a challenge, the chances are good that we've seen a version of it before, and we know what worked and what didn't.

The toolkit that comes with that experience is broad. On any given day, our teams are managing on-site embedded workforce programs, coordinating global talent supply chains through MSP arrangements, executing outcome-based project work with defined deliverables, and integrating AI tools to improve sourcing speed and candidate quality. AI has become standard infrastructure in staffing operations, with most mid- to large-sized employers now using AI-enabled tools somewhere in their hiring process, and staffing firms have been among the earliest adopters. The goal across all of it is the same: move past the question of how to fill a seat and get to the question of what outcome the organization is actually trying to drive.

What to look for in a staffing partner

The difference between a staffing vendor and a true workforce solutions partner shows up in your business results. A bad hire is costly, and the right partner reduces that risk by bringing insight and strategy to every engagement. Here's what separates the ones worth partnering with from the rest.

How a staffing relationship grows over time

The most expansive workforce partnerships don't start that way. They start with one order.

Here's how it often goes. A client brings Kelly in for temporary industrial workers at a single location. Trust builds, and six months later they ask if we can put someone on-site to manage the program. Then they want support for their IT team. Then bundled statements of work across three divisions. Then a global MSP arrangement coordinating vendors across multiple geographies. None of that was in the original conversation; it grew because the foundation was solid.

That progression is an argument for choosing your initial partner carefully. The agency you bring in for a single need may become deeply integrated in how your workforce operates.

Finding the right workforce partner for your organization

Kelly founded the modern staffing industry in 1946. In the eight decades since, we've helped organizations face every major workforce shift, from the post-war labor market to the rise of the internet and the AI-driven changes reshaping work today. When the ground is moving, we know how to help clients stay ahead of it.

If you're ready to think differently about how your workforce is structured and supported, we welcome the conversation.