Housing projects have an impact on personal, socio-economic as well as political conditions. As a result,rnit is essential to assess the actual causes of delay and constraint in order to minimize the delays and theirrncorresponding costs and time. Successful completion of projects leads to socio economic growth and helpsrnto provide good social welfare. The objective of this thesis is to investigate the main causes of delays andrnconstraints as well as effects of delays in AAHDPO project. The study were used both Primary andrnsecondary data sources to collect the necessary information. Two type of sampling techniques werernused namely random and purposive sampling. Two Projects specifically Koye feche (10/90) and Kiletorn(20/80) were selected randomly based on the lists from HDPO office. The respondents were contractors,rnconsultants and clients who worked in the Koye-feche and Kileto projects. The structured questionnairernin Likert scale was distributed and collected at a selected site of the case study. There are many causesrnthat induce delay in HDPO construction projects. Before identifying the causes of delays the study was torntest whether delay in HDPO had been found/ existing or not. From the above sample survey resultsrnunderstand that more than 78.18 percent of the respondents agreed the HDPO construction is exposed torndelay. Moreover, Interviews conducted with some of the officials in HDPO indicated that delay is thernmain challenge for construction projects. The relative important index (RII) was computed for each causernto identify the most significant causes and later the causes of delays were ranked based on the RII; resultsrnshowed that the ten critical factors that contribute to project delays in HDPO are; delays in the paymentrnfor services, Shortages in basic materials, Slow decision making by all functional group, inaccurate costrnand time estimate, poor infrastructure development, poor capacity of contractor and sub-contractor, Poorrnrisk management and inadequate financial availability as planned through project duration. The criticalrneffects of delays are time overrun, cost overrun, litigation/ legal action, Public dissatisfaction or loss ofrnbelief of citizen, termination and disputes. After the causes and effects could be observed and provide arnclue to minimizing delay on construction sites. This study has also delivered recommendation, all of thatrnwill assist client organizations to curb the problems associated with delays and constraints in its projectrnimplementation.rnKey words: constraints, delay, cause, effect, mitigation, construction, project implementation