The Nigerian prisons have suffered a lot of pitfalls in the past. This is largely as a result of neglect and mismanagement of resources and misplaced value of inmates which results in congestion of prison institutions. The study there fore assesses the causes and effects of congestion in Nigeria. Related literatures were reviewed on the subject matter. The findings of the study indicated that the Gboko prison is congested. The congestion is basically caused by: court delay, poverty level of inmates. It was revealed that prison congestion brings about poor feeding of inmates, low medical attention, as well as encourages inmates to learn more criminal skills. Based on the findings made during the course of research, recommendations were made: there should be supervision on judges to make speedy judgement, judges should take into cognizance the capacity of the prison before passing sentences, and alternatives to imprisonment should be used in place of actual imprisonment. In conclusion, Government should ensure that recommendations posited in this research are adequately addressed to reduce prison congestion in Nigeria, particularly Gboko Medium Security Prison, Benue State.