The present investigation was carried out to assess the mud crab fattening system and the socio-economic condition of crab fatteners. The survey was conducted during October to November 2017 in Rampal Upazila under Bagerhat district. Data were collected through survey of randomly selected 40 crab fatteners through questionnaire interview and focus group discussion. It was reported that the peak fattening season of male crab was in dry season (October–May) whereas the peak fattening season of female crab was in wet season (June–September). In the study area, fatteners usually used 95 gm-215gm crab seed for fattening. The average stocking density was 67pieces/ decimal. About 25% fatteners used tilapia feed for stocked crabs. Fattening is usually done for 2-4 weeks. The average production was 14.36 kg/decimal and net benefit was 15,230 TK/Yr/decimal according to the cost–benefit analysis. There were 30% crab fatteners were belongs to the age group of 41-45 years, who were the main working force in the society. Among the fatteners 67% were Hindus. Forty two percent (42%) of crab fattener’s monthly income range was BDT 16000-30000. In the study area, 45% fatteners were found to live in tin shed house and only 27% of fattener used pacca toilet. The 35% of the crab fatteners were up to class 10 pass. Fifty percent fatteners were depends on upazila health complex for their treatment. Most of the crab fatteners take loan from the money lender. According to the survey, most of the crab fatteners increased their income level through crab fattening but housing and sanitary condition was not developed proportionate to the income. Crab fattening is gaining popularity day by day because it is a very easy, profitable and takes less time. However, the fatteners are still practices old fattening system. It is needed to introduce recent update system and feeding system following other countries.