Provided are an imaging unit, an imaging module, and an endoscope system that make it possible to achieve a reduced diameter of a distal end of an insertion section and to obtain a high-quality image. An imaging unit 10 according to the present invention has a semiconductor package 20 which includes an image sensor and a connection electrode 21 formed on a face f2, a first multi-layer substrate 30 which includes connection electrodes 31, 33 formed on faces f3 and f4 and is connected to the semiconductor package 20 through the connection electrode 31, a second multi-layer substrate 40 which is connected to the first multi-layer substrate 30 with a layer direction of the second multi-layer substrate 40 perpendicular to a layer direction of the first multi-layer substrate 30, an electronic component 51 which is mounted inside the first multi-layer substrate 30, and a cable 60 which is connected to the second multi-layer substrate 40. The second multi-layer substrate 40 is connected to the first multi-layer substrate 30 to form a T shape, and the first multi-layer substrate 30 and the second multi-layer substrate 40 lie within a projected plane in an optical axis direction of the semiconductor package 20.
