BACKGROUND: N,N-Diethyl-3-methylbenzamide (DEET) topical mosquito repellents are effective personal protection tools. However, DEET-based repellents tend to have low consumer acceptability because they are cosmetically unappealing. More attractive formulations are needed to encourage regular user compliance. This study evaluated the protective efficacy and protection duration of a new topical repellent ointment containing 15% DEET, MAÏA® compared to 20% DEET in ethanol using malaria and dengue mosquito vectors in Bagamoyo Tanzania. METHODS: Fully balanced 3 × 3 Latin square design studies were conducted in large semi-field chambers using laboratory strains of Anopheles gambiae sensu stricto, Anopheles arabiensis and Aedes aegypti. Human volunteers applied either MAÏA® ointment, 20% DEET or ethanol to their lower limbs 6 h before the start of tests. Approximately 100 mosquitoes per strain per replicate were released inside each chamber, with 25 mosquitoes released at regular intervals during the collection period to maintain adequate biting pressure throughout the test. Volunteers recaptured mosquitoes landing on their lower limbs for 6 h over a period of 6 to 12-h post-application of repellents. Data analysis was conducted using mixed-effects logistic regression. RESULTS: The protective efficacy of MAÏA® and 20% DEET was not statistically different for each of the mosquito strains: 95.9% vs. 97.4% against An. gambiae (OR = 1.53 [95% CI 0.93-2.51] p = 0.091); 96.8% vs 97.2% against An. arabiensis (OR = 1.08 [95% CI 0.66-1.77] p = 0.757); 93.1% vs 94.6% against Ae. aegypti (OR = 0.76 [95% CI 0.20-2.80] p = 0.675). Average complete protection time (CPT) in minutes of MAÏA® and that of DEET was similar for each of the mosquito strains: 571.6 min (95% CI 558.3-584.8) vs 575.0 min (95% CI 562.1-587.9) against An. gambiae; 585.6 min (95% CI 571.4-599.8) vs 580.9 min (95% CI 571.1-590.7) against An. arabiensis; 444.1 min (95% CI 401.8-486.5) vs 436.9 min (95% CI 405.2-468.5) against Ae. aegypti. CONCLUSIONS: MAÏA® repellent ointment provides complete protection for 9 h against both An. gambiae and An. arabiensis, and 7 h against Ae. aegypti similar to 20% DEET (in ethanol). MAÏA® repellent ointment can be recommended as a tool for prevention against outdoor biting mosquitoes in tropical locations where the majority of the people spend an ample time outdoor before going to bed.