Can you negotiate a job offer after accepting it verbally?

Not with me, you can't.  If you accepted it, either you are coming on board as agreed or you are turning it down. You hit the nail on the head with "unprofessional" - which isn't a matter of science, but I think you'd be hard pressed to find anyone who felt a potential hire going back on his word demonstrated any kind of desirable trait to have in an employee.

In general it is not a recommended practice but it depends what exactly your negotiation is all about. If you are negotiating on the terms which are clearly told to you during the verbal offer call and then you negotiate after giving your consent does not give a right impression on you as a reliable candidate. But if you are going to negotiating on things which are not discussed during the call or not aware during the call then it is fine. For example if the company mentioned about relocation allowance but not the figure and later you feel there is something better can be done, then you can discuss about that.

Handshakes and verbal acceptances are socially and culturally binding. If you don't have enough information, the offer isn't to your liking, or you have other opportunities in the pipeline, *just negotiate for more time and money upfront*. I've seen people try and renegotiate after accepting with full intent of still going to the company.  The results are rarely pretty. This is one of the few situations where you have negative leverage. A few examples I can think of: > Engineer simply told "no renegotiating". > Offer got straight up rescinded. Deserved, in my opinion. > Offer got renegotiated - downwards. Yes, the hiring manager actually talked down the dude, who actually lost a chunk of equity after he tried to renegotiate post-acceptance (he ended up taking the lower offer). A comically bad outcome. Basically - don't do this. The *only* times I would consider this acceptable is when meaningful new information enters the system: Another company offers a meaningful amount more comp and you weren't rampantly offer-hunting afterwards (a meaningful amount higher - 3x to 5x - not some 10k to 20k dog treat). You have a visa issue. You have a significant personal situation shift that impacts your ability to work at the company. You find out you were *meaningfully screwed* (maliciously). Of course, you feel if this has happened, you should just not work for the company! But, all this is reasonably stuff you should be aware of as early in the process as possible. If you withhold information like this, this is unfair to the company, and your own integrity. To repeat - don't do it. Just negotiate on all dimensions more aggressively upfront.