The study investigates the effect of fintech integration on bank efficiency across 59 developing nations from 2010 to 2022. The analysis also considers bank size, capitalization, ownership, competition, and financial sector development. We construct two indicators of fintech integration at the bank level and discover a non-linear relationship between fintech and efficiency. While fintech integration initially hampers bank efficiency, further adoption beyond a certain point enhances it, exhibiting a U-shaped relationship. Moreover, larger, well-capitalized, foreign-owned banks and those operating in more competitive and developed banking sectors exhibit a shallower initial decline in efficiency and a quicker transition to the efficiency-enhancing phase of fintech integration.