How long does it take to hear back from an agent if they're interested?

It's really difficult to say. Since picture books are typically included with the query in their entirety, that means you won't have to wait for them to request a partial and/or a full -- they can accept or reject off the query itself. I'd say give them at least 8 weeks, but also know that MANY agents have a "no response means no" philosophy.

Also, it's really, really difficult to get an agent for a single picture book. Because the royalties will be split between you and the illustrator, a single title doesn't really earn an agent enough money to bother. Picture books are actually one area where you may be better off submitting directly to publishers.

Here, by the way, is a good blog post by an agent about picture books:
http://literaticat.blogspot.com/2011/07/whole-lot-of-info-about-picture-books.html

jasperd said:

I've sent it to several agents (unsolicited) about three weeks ago and have gotten three rejections via form letter.

I know typically, it could take up to three months or more but isn't that when they're not interested?

I'm just worried, being a new writer, that I've unknowingly done something to kill my chances with this book and if nobody tells me what I'm doing (or not doing), I'll never get published.

Click to expand...

Three weeks is a very short time in publishing. And it depends on the agent and their schedule regarding when they will get back to you. I had full requests after a day, few weeks, three months. I've had rejections in ten minutes, a few days/weeks/months. Some agents never got back to me. Some agents with my full never got back to me. QueryTracker helps a lot to give you an average wait time.

If you don't hear back after whatever QT says is the norm (one to three months) I'd nudge or resend the query.

Don't worry about doing something to "kill your chances". Unless you act like a psychopath/sociopath, the only thing your book will be judged on is its own merits.

I hope this helps! Good luck!

Have you tried posting in SYW? Maybe someone can help identify if you have made any mistakes.

I agree with the others though that three weeks is not very long.