Cancer diagnosis and treatment are of great interest due to the high death rate of cancer. To improve the cure rates of cancer, a diagnostic tool which can detect and treat cancer at initial stages is great needed. Laser-induced fluorescence (LIF) is an adequate analytical technique with advantages of high sensitivity, low sample consumption, short testing time, and suitable for in situ testing. Therefore, it has become one of the most widely used spectroscopic methods for cancer in vivo diagnosis in recent years. This review mainly focuses on the applications of in vivo LIF to distinguish premalignant, malignant from normal tissues in a variety of organ systems, such as lung breast, colon, cervix, esophagus, and bronchus. The potential influence factors for cancer diagnostics and the subsequent suitability of the method to different applications are well discussed. Meanwhile, the technical merits and weaknesses of the LIF technology for cancer diagnosis are also evaluated. Furthermore, different exogenous fluorophores, endogenous fluorophores, and fluorophores synthesized in the tissue are compared on their active principle and effect contrast. The technical potentials of LIF for further development and future applications are also presented as well in this review.