The study examines communication and corporate social responsibility in Shell Petroleum Development Company and Mobile Producing Nigeria Unlimited. It was aimed to find out the specific means or strategies adopted by Shell and Mobile in their communication with host communities. It was also to find out degree to which Shell and Mobile interact with various groups such as women group, Youths and community leaders in their host communities. It was to further determine the perception of host communities in the effectiveness or otherwise of Shell and mobile corporate social responsibility effectiveness. The survey method was used with the questionnaire as instruments for data collection. The sample size was drawn from eight communities in Bayelsa state of both companies. Altogether, eight hundred and eighty six people were sampled. The data collected were analyzed using mean for the research questions. The research found out that Shell and Mobil's major means of communication with host communities are the face to face newspaper interactions with youths as fair. It was also found out that Shell and Mobil frequently interact with chiefs and that the communication encounters are more during crisis period. To engender harmonious relationship, Shell and Mobile should continue to enlarge their capacity for interacting with human groups through interpersonal, small groups and public communication strategies. The companies should give attention to segments of the communities according to their strength members and importance to company operation. Finally, while it is dangerous to interact frequently, routinely and regularly, Shell and mobile should plan to be more proactive and not reactive to community issues