Objective: The aim of this study was to investigate the effects of 960 nm diode laser and acidulated phosphate fluoride on calcium solubility of human dental enamel. Background Data: Interest in diode lasers has grown steadily since its invention due to its inherent advantages and its range of applications. Several other laser types have shown good results in caries prevention; however, there are few studies on dental tissue interactions using diode lasers. Methods: Acid resistance was evaluated using 65 enamel specimens, divided into five groups: control (C), fluoride (F), laser (L), laser + fluoride (LF), and fluoride + laser (FL). The laser was operated using the parameters of 6.5-W peak power, 5-msec pulse duration, 10-Hz repetition rate, and 33-mJ pulse energy. These parameters were previously tested regarding pulpal temperature rise and enamel morphology, and were determined to be safe. The amount of calcium lost during demineralization was measured. Results: The calcium solubility of the laser group was 12% higher than of the control group ( p > 0.05). Group F showed a 33.6% increase of acid resistance ( p < 0.05). When laser was associated with fluoride, the calcium solubility increased significantly ( p < 0.05) compared to both the control group and the laser group. Groups treated with fluoride showed the same results ( p > 0.05). Conclusion: The 960-nm diode laser promoted a slight increase in calcium solubility. A statistically significant reduction on calcium solubility was achieved with the three treatments that involve fluoride (F, FL, and LF). The additional application of laser irradiation did not cause any significant increase or decrease in calcium solubility.