The "Action Plan for the Optimization of the Fish Lift built at the Touvedo Hydropower Plant" took place between September 2011 and February 2014, and consisted of three stages: stage 1 – evaluation of fish lift use and assessment of its efficacy; stage 2 - hydraulic characterization of the lift entrances and implementation of mitigation measures to improve fish lift operation; stage 3 – re-assessment of the efficacy of the fish lift after implantation of measures. Overall, the lift was used by 10011 fish, being the European eel (50.7%) and the northern Iberian nase (37.5%), the most abundant species. After the implementation of measures, a significant increase was observed in the number of fish that used in the lift, from 3389 (stage 1) to 6272 (stage 3), being the European eel the species which most contributed to this increase. Fish lift selectivity was low, being all species recorded with the exception of the ruivaco, a small resident cyprinid. The hydraulic characterization of fish lift entrances revealed that entry conditions are attractive for all the species, particularly for the larger size-classes, when the powerhouse is off or at full load. Contrarily, when the dam is operating at half-load, conditions are unattractive due to the presence of recirculation areas and negative velocities that may hinder fish entrance. Ten measures of different nature and priority were proposed, most of which were implemented. The comparison of the results between stage 1 and 3, indicated that 4 of the measures contributed to the increase of the fish lift efficacy, including the reduction of the gap width. The results obtained, allow us to conclude that the Touvedo fish lift contributes positively to the maintenance of the cyprinid, trout and eel populations, though the true efficacy of downstream movements is still inconclusive for this latter species.