An environmental uncertainty challenges today’s bus iness managers since higher environmental uncertainty is likely to drive Small, Micro and Med ium Enterprises (SMMEs) to change business processes. This paper argues that paying more atten tion to strategic information systems planning (SIS P) may increase survival rates of SMMEs, thus supporti ng the contention that SISP is of significant importance if SMMEs are to remain competitive. This reduces the environmental uncertainty influence on those managing SMMEs. In a postal survey to asse ss SISP and environmental uncertainty, a questionnaire measuring three constructs namely str ategic information systems planning process (SISPP), strategic information systems planning suc cess (SISPS) and environmental uncertainty, was used. Empirical evidence was collected from109 head s of information systems and IT executives. From 15 sub-hypotheses, 9 were supported and 6 not suppo rted. The results suggest that some SISPP phases are more effective in different environment and the se phases can lead to the SISPS under environmental uncertainty. Based on the empirical evidence, the pa per concludes that the South African SMMEs sector is generally not out of environmental uncertainty influence.