An insert according to an embodiment of the present invention includes an upper surface, a lower surface, a side surface which is connected to the upper surface and the lower surface, and includes a first side surface, and a cutting edge which is located an intersection of the upper surface and the side surface, and comprises a first cutting edge corresponding to the first side surface. The first cutting edge has a projected shape projected toward the upper surface in a side view, and has a recessed shape recessed inward in a top view. A cutting tool according to an embodiment of the present invention includes the insert and a holder configured to attach the insert thereto so that at least a part of the first cutting edge has a negative axial rake angle. A method of manufacturing a machined product according to an embodiment of the present invention is a method of manufacturing the machined product by using the cutting tool.