Cannibalism is an intra-specific predation often resulting in massive mortality in intensive cultured fish species. In piscivorous species, the onset of predation is inevitable. This study explored the link between predation abilities and the onset of cannibalism in pikeperch larvae, a top predator species, with a potential for the European inland aquaculture. Cannibals and non-cannibals, aged between 17 and 34 days-post-hatching, were tested to compare their predatory behavior using zebrafish and pikeperch larvae as prey. Each tested fish was confronted with three other fish (pikeperch or zebrafish) (n = 204 tests) in an arena (20 × 7 × 4 cm with 2 cm of water height, 280 mL) and their behavior was recorded for 20 min. The normal predatory behavioral sequence (orientation, approach, attack and capture) was much more efficient in cannibals (calculated as the ratio of number of captures on the number of attacks) than in non-cannibals in both the predation (0.31 ± 0.28 vs. 0.05 ± 0.15; padjust < 0.0001) and the cannibalism (0.21 ± 0.29 vs. 0.02 ± 0.08; padjust = 0.0006) tests. The shift to a piscivorous diet involved a modification of the attack tactic, replacing a “S-shape” by an attack without “S-shape” but with a tail propulsion. This second tactic developed earlier in cannibals whereas non-cannibals are only able to perform the “S-shape” attack used during the first days of life. Cannibalism was linked to the onset of an efficient piscivory behavior.