The study applied institutional theory to investigate socio-environmental factors [coercive pressures (CPs), normative pressures (NPs) and mimetic pressures (MPs)] influencing the use of e-learning by teachers of tertiary institutions in Nigeria. Survey research design was adopted. Purposive sampling was used to select three tertiary institutions, and proportionate to size sampling was used to select the respondents. Data were collected using a questionnaire. Frequency distribution and percentages, as well as multiple regressions were used for data analysis. The results revealed that CPs, in contrast to NPs and MPs had no significant relationship with attitude and intention to use e-learning. Attitude had a significant relationship with intention to use and also mediated between institutional forces and intention. Gender and age did not have significant relationships with intention but income had. NPs had the greatest impact on attitude and intention. The study demonstrated the importance of socio-environmental factors on adoption and use of e-learning in tertiary institutions in Nigeria.