An attachment structure for an in-vehicle camera includes a first bracket and a second bracket. The first bracket is fixed to an inner surface of a windshield. The second bracket holds an in-vehicle camera when the second bracket is attached to the first bracket at an attachment position. The first bracket includes a support portion and a first one-way engagement portion. The second bracket includes a pressing portion and a second one-way engagement portion. The pressing portion presses a pressed portion of the in-vehicle camera against the support portion and holds the pressed portion between the pressing portion and the support portion when the second bracket is at the attachment position. The second one-way engagement portion cooperates with the pressing portion to inhibit the second bracket from moving with respect to the first bracket when the second one-way engagement portion is engaged with the first one-way engagement portion.