There are provided an imaging device, a focusing control method, and a focusing control program which are capable of realizing focusing control at a high speed with high accuracy. A digital camera includes an imaging element 5 that has pixels including phase-difference detecting pixels 52A and 52B and images a subject through an imaging optical system including a focus lens, and a system controller 11 that selectively performs focusing control using a phase difference AF method or focusing control using a contrast AF method in a mode in which focusing control for focusing on a main subject by driving the focus lens is continuously performed multiple times. The system controller 11 performs the focusing control using the contrast AF method in a case where a state in which a degree of reliability of the focusing control using the phase difference AF method is equal to or less than a threshold value persists N times (N is a natural number of 2 or more) while the focusing control using the phase difference AF method is continuously performed.