The title compound, C15H11BrClN3, is built up from a planar imidazo[4,5-b]pyridine unit linked to phenyl and allyl substituents. The allyl substituent is rotated significantly out of the imidazo[4,5-b]pyridine plane, while the benzene ring is inclined by 3.84 (6)° to the ring system. In the crystal, mol­ecules are linked via a pair of weak inter­molecular C—H...N hydrogen bonds, forming an inversion dimer with an R22(20) ring motif. The dimers are further connected by π–π stacking inter­actions between the imidazo[4,5-b]pyridine ring systems [centroid–centroid distances = 3.7161 (13) and 3.8478 (13) Å]. The important contributions to the Hirshfeld surface are H...H (35.9%), H...Cl/Cl...H (15.0%), H...C/C...H (12.4%), H...Br/Br...H (10.8%), H...N/N...H (7.5%), C...Br/Br...C (5.9%), C...C (5.5%) and C...N/N...C (4.0%) contacts.