The aim of the study was to identify determinants of smallholder fruit commercialization in southwest Ethiopia. To get the sampled respondents multi-stage sampling techniques were used and in view of that, three districts were selected purposively from Jimma zone by selecting eight kebeles randomly. At the end, total of 240 sample households were randomly selected from these kebeles. To answer the research questions and objective of the study both qualitative and quantitative data were collected from primary and secondary sources. The primary data were collected from fruit producers as sampled households, agricultural experts, local leaders and other subject matter specialists on various aspects of commercializing fruits. Primary data were collected from the respondents using a pre-testing questionnaires, structured interview schedule and closed and open-ended questionnaires by well-trained enumerators closely supervised by the researchers. Secondary data were previous research findings and reports collected from kebeles, districts, agricultural offices, ministry of trade, trade and revenue offices. Moreover, qualitative data were collected through discussions with different agents by using focus group discussion and key informant interviews. The collected data were analysed using descriptive statistics (frequency, percentage, average mean, standard deviation, chi square and t-test) and econometric model (Probit model) to analyse determinant factors affecting smallholder’s participation decision in marketing of fruits. From the result, age of household heads, household family size, access to transport services, off-farm activities, access to extension services, distance to market, improved fruit seeds and perishability of fruit were significantly affecting smallholder farmer’s participation decision in commercialization of fruits. Therefore, to overcome the investigated problems strong commitment and reformation should be done by stakeholders including farmers, extension agents, researchers, policy makers.