The antagonistic potential of Trichoderma longibrachiatum against the pathogen Botrydiplodia theobromae was examined in vitro. Both fungi were paired on 9 cm Petri plates of acidified potato dextrose agar (APDA). Three pairing methods were employed, viz., ‘inoculating antagonist before pathogen’, ‘inoculating pathogen before antagonist’ and ‘simultaneous inoculation of pathogen and antagonist’. Radial growth (cm) of both fungi were later analysed using the GLM Procedure of SAS. Growth inhibition of B. theobromae by T. longibrachiatum in all pairing methods was significantly different from control (P = 0.05, R 2 = 0.89). Growth inhibition of the pathogen was best when using ‘inoculation of antagonist before pathogen’. Duration of pairing (DAP) and pairing method are both critical to significant antagonistic impact of T. longibrachiatum on B. theobromae (P > 0.0001). Inhibition mechanism includes competition for space and nutrients. T. longibrachiatum could thus be a promising antagonist of B. theobromae.