You worked alongside this person for three years. You know how they run a meeting, they know how you handle a deadline that slips, and now their name sits on a job posting as the hiring manager. The instinct is to write a warmer, more personal letter than usual. It is usually the wrong instinct.
The letter gets shorter, not warmer
When the reader already knows your work, most of what a cover letter normally does becomes redundant. You do not need to prove you are reliable or calm under pressure. They watched you do it, or watched you fail to, and no paragraph will overwrite that memory.
So the job of this letter changes. It is no longer an introduction. It is an update. The only genuinely new information you can hand this person is what has happened since you last worked together:
- Scope. Did you go from running one account to running a portfolio? From a team of four to a team of twelve?
- Skills. What can you do now that you could not do when they knew you? A new stack, a certification, a language, budget ownership.
- Results since. Numbers from your last role or two, the ones they have no way of knowing.
A good version of this letter is often noticeably shorter than a standard one, sometimes by a third. That is fine. Padding it with adjectives about your work ethic reads oddly to someone who has seen your work ethic up close, and they will notice.
Your former colleague knows who you were. The letter exists to tell them who you are now.
Name the relationship once, in the first line
Yes, mention it. Hiding the connection is strange when they will recognise your name in the pile anyway, and if someone else on the panel learns about it later, your silence starts to look like a tactic.
Mention it once, factually, and move on:
"We worked together on the payments team at Northbeam from 2019 to 2022, where I led QA for the checkout rebuild you were managing. I am applying for the Senior Test Lead role on your team."
That sentence dates the relationship, defines what each of you did, and states the application. Then leave it alone. Do not return to the shared history in the closing paragraph with "I would love to work with you again." One mention is context. Three mentions start to look like you are asking for a favour.
Keep the register professional even if you were on first-name, pub-on-Friday terms. The letter is a document that gets forwarded, and nobody in HR should feel they have walked into a private conversation.
Write for the reader who does not know either of you
This is the part people forget. Your former colleague may be the hiring manager, but they are rarely the only reader. The letter passes through HR screening, maybe an ATS, and often a panel member from another department who has never heard of you and has no idea the two of you shared an office.
That reader needs to understand the letter without any backstory. So cut:
- "As you know..." They might. The HR partner does not.
- Nicknames, project codenames and in-jokes. "The Friday fire drill" meant something to your old team. To a stranger it is noise.
- References to shared people. "Say hi to Dana" belongs in a private message, not a document that gets passed around.
A useful test: hand the draft to a friend who has never met your former colleague. If any sentence makes them ask what it means, rewrite it in plain terms. Name the company, describe the project in generic words, give the result.
There is a second reason for this discipline. Many hiring managers are wary of looking like they favour a friend, and some companies require them to declare any prior relationship with a candidate under a conflict-of-interest policy. A letter that reads as neutral and evidence-based makes it easier for them to argue for you in front of others. A chatty one makes it harder.
When the hierarchy has flipped
The awkward version of this situation is a reversal. Two cases come up often enough to deal with separately.
You were senior to them
You used to review their work. Now they would review yours. The risk here is tone, and it goes wrong in two opposite directions. Some candidates slip back into the old dynamic without meaning to ("I always knew you would go far"), which sounds patronising. Others overcorrect with heavy deference, which sounds false.
Treat them as what they are now: the person hiring for the role. Address their current problems, not your past responsibilities. One line can settle the question everyone on the panel is quietly asking: "I am applying for an individual contributor role and I am clear on what that means." That is enough. No speech about ego or hierarchy.
Do not mention that you trained them, hired them or pushed for their promotion. Even if it is true, it puts them in an uncomfortable position if the letter is shared.
They were junior to you, and your path has been slower
Sometimes the reverse applies: they moved up quickly and you did not. The temptation is to explain your pace. Resist most of it. If there is a clear reason (a career break, a sector change, a deliberate move to a smaller company), say it in one sentence in the body. Otherwise, focus on what you bring to this role today. They are not grading your trajectory. They are filling a seat.
Should you message them before you apply?
In most cases, yes. A short note before you submit is courteous and practical. It prevents the surprise of seeing your name appear in the applicant list, and it lets them flag a process issue you should know about, such as a recusal rule or an internal candidate already in the frame.
Keep it brief and give them an easy exit:
"Hi Sam, I saw the Test Lead opening on your team and I plan to apply through the careers page this week. Wanted you to hear it from me first. No need to do anything, and if there is a reason it would be awkward, just tell me."
What not to do:
- Do not ask them to skip the formal process for you. That puts them in a compromising position.
- Do not attach your CV and ask for feedback. You are asking a hiring manager to pre-screen you privately.
- Do not treat a friendly reply as a promise. They can be warm in a message and still have to follow a scoring grid in the panel.
Then apply through the normal channel, with the same quality of CV you would send to a stranger. If the company asks the hiring manager to step back from part of the decision, your file lands with people who have never met you. One more reason the CV and letter must stand on their own.
What the letter looks like, section by section
Here is a structure that works in most cases:
- Opening (two sentences). The relationship, dated and defined. The role you are applying for.
- What changed (one paragraph). Scope and skills since you worked together, stated concretely.
- Evidence (one paragraph). Two or three results from your recent roles, with numbers where you have them. Pick results that map directly to the job posting.
- Fit (two or three sentences). Why this role and this team, now. This is where knowing the manager genuinely helps, because you can name the team's real problems without guessing.
- Close (one sentence). Availability and a plain sign-off.
That is the whole letter. No paragraph on your values, no nostalgia about the old project.
Your CV needs the same update logic. If your LinkedIn profile is more current than your CV, a tool like Postulit can turn the profile into a clean, recent CV so the document backs up what the letter claims. A former colleague will spot a CV that still describes the job you held when you sat two desks away.
The takeaway
Before you send the letter, run one check: highlight every sentence containing something your former colleague already knew before reading it. Delete most of those, keep the single opening line about your shared history, and make sure what remains is new, specific and readable by a stranger on the panel. If the letter shrinks by a third, it is probably better.