The researchers investigated the effect of morality training technique on cohabitation behaviour among undergraduate students in Imo state university, Owerri. The pre-test, post-test, control group quasi-experimental design was adopted for this study. Two research questions and two null hypotheses tested at 0.05level of significant guided the study. The population of this study comprised 8,031 of 300 level students in Imo state university, Owerri. The researchers sampled 60 students for the study. The sampling techniques employed are purposive and cluster. Two instruments developed by the researchers were used for data collection, namely: Students Cohabitation Identification Scale (SCIS) and Cohabitation Detecting Scale (CDS). The instruments were validated by expects in Departments of Measurement and Evaluation as well as Guidance and Counselling. The reliability of the instruments was ascertained through test-retest method using Cronbach alpha statistics which yielded reliability coefficients of 0.81 and 0.85 for SCIS and CDS respectively. Data collected were analysed using mean score and standard deviation to answer the research questions. The hypotheses were tested using the analysis of Covariance (ANCOVA) at 5% level of significance. The findings revealed among others that morality training technique (MTT) is significantly effective in the reduction of cohabitation among undergraduate at post-test and follow up test. From the above findings, it was recommended among others, that Counsellors should make use of morality training technique in curbing cohabitation behaviour among undergraduate students to enhance their academic performance.