While self-etching dental adhesives are considered user friendly, their application is still technique-sensitive, especially considering the need of solvent evaporation during clinical used and the presence of water on the dentin substrate. The present study aimed to evaluate the influence of 10-metacryloxydecyl dihydrogen phosphate (10-MDP) concentration on the degree of conversion (DC) of adhesives containing a three-component photoinitiator under distinct manipulation protocols. Adhesives containing a three-component photoinitiator system (camphorquinone/1.2-diaminobenzene/iodonium salt) were prepared and different 10-MDP concentrations were added (0 wt%, 3 wt%, 6 wt%, 9 wt%, 12 wt%, and 15 wt%). Four protocols were evaluated: I) Control (without manipulation), II) 5 s of solvent evaporation with compressed air, III) 20 s of evaporation, and IV) addition of water to the adhesive to simulate the humidity of dentin in the oral environment. DC was evaluated by FTIR-ATR. Each adhesive (≈12 μL, n = 12) was dropped and tests were run before and after light-activation. Data were analysed with two-way ANOVA and Tukey's HSD (α = 0.05). Adhesives and protocols were statistically significant factors, as well as their interaction (p < 0.0001). The analysis of interaction indicates that 12% 10-MDP adhesive with water addition presented the highest DC with 92.79%, while the 10-MDP-free adhesive with 20 s evaporation had the lowest DC of 70.75%. The presence of water has increased DC for all groups, except for the MDP-free adhesive. These results suggest that 10-MDP can adjunctively increase the DC of three-component-photoinitiator adhesive and water did not seem to affect the DC in the presence of such monomer. • The polymerization of dental adhesives increases with the addition of 10-MDP. • The presence of water may not negatively influence the DC of adhesives containing 10-MDP and an iodonium salt. • The air-blowing may influence the DC of experimental adhesives evaluated.