Substance abuse is a problem to some serving police officers and hence delivering poor services to members of the public. The problem could be contributed to by stress and other occupational situations. However, the sub-cultural setup of the policing career contributes to this vice in order to reduce stress. It is also reported that cases of suicides and domestic violence among the police officers is attributed to drug abuse. The study, was purposed to find out the correlation between substance abuse and service delivery by the Kenya Police officers in Nairobi City County. The study shed light on measures that are viable and can be taken to ensure proper service delivery and to curb substance abuse among the Police Officers. The objectives are; establish the extent of substance abuse by the Kenya Police Officers in Nairobi City County; identify the drivers of substance abuse among the Kenya Police Officers in Nairobi City County; establish the effects of substance abuse on service delivery by the Kenya Police Officers in Nairobi City County and investigated the strategies that could be used to control substance abuse by the Kenya Police Officers in Nairobi City County. This study used a cross-sectional study design. Cross-section design looks at a portion of the population at one point in time. For this study, different cadres of police in Nairobi City County were the target population.2350 participants were sampled to participate in the study with a sample of 235 being used. Questionnaires were used for data collection which was administered by the researcher. Analysis of quantitative data was done using descriptive statistics with the help of Statistical Package for Social Sciences, version 23. Qualitative data was processed and analysed according to their content and segmented into themes. Secondary data was also be used from the police data to get information on matters of police turns over, absenteeism, disciplinary cases among others that relate to substance abuse. Both descriptive and inferential statistics were used to make sense out of the data. The findings show that police officers attend the job when they abuse the drug. The results also indicate that abuse of drug affect the performance of police in service delivery and productivity. The result indicates that there was significant relationship between dependent variable (service delivery) and independent variable (Level of productivity, Type of service delivery and Absenteeism) since the P-value is less than 0.05. It was concluded that partial and full absenteeism (lost man hours/ lost labour days) cost the police department as a government a lot of money at the police force. From the findings of this study, it is concluded that alcohol and drug abuse impact negatively on the service delivery among police officers. Also, Exposure or awareness of alcohol advertising may lead to heavier or more frequent abuse of drug among police officers adults. The study recommends that there is need for the law enforcement sector in liaison with stakeholders to institute stringent policy mechanisms and capacity development programmes to curb alcohol and drug abuse among police officers.