A study of B + c → K + K − π + decays is performed for the first time using data corresponding to an integrated luminosity of 3.0     fb − 1 collected by the LHCb experiment in p p collisions at center-of-mass energies of 7 and 8 TeV. Evidence for the decay B + c → χ c 0 ( → K + K − ) π + is reported with a significance of 4.0 standard deviations, giving σ ( B + c ) σ ( B + ) × B ( B + c → χ c 0 π + ) = ( 9. 8 + 3.4 − 3.0 ( stat ) ± 0.8 ( syst ) ) × 10 − 6 . Here B denotes a branching fraction while σ ( B + c ) and σ ( B + ) are the production cross sections for B + c and B + mesons. An indication of ¯ b c weak annihilation is found for the region m ( K − π + ) < 1.834     GeV / c 2 , with a significance of 2.4 standard deviations.