Neuraminidase (NA) is an important protein for the replication cycle of influenza A viruses. NA is an enzyme that cleaves the sialic acid receptors; this process plays a significant role in viral life cycle. Blocking NA with a specific inhibitor is an effective way to treat the flu. However, some strains show resistance to current drugs. Therefore, NA is the focus for the intense research for new antiviral drugs and also for the explanation of the functions of new mutations. This research focuses on determining the profile of variability and phylogenetic analysis and finding the correlated mutations within a set of 149 sequences of NA belonging to various strains of influenza A virus. In this study, we have used the original programs (Corm, Consensus Constructor, and SSSSg) and also other bioinformatics software. NA proteins are characterized by various levels of variability in different regions, which was presented in detail with the aid of ConSurf. The use of four independent methods to create the phylogenetic trees gave some new data on the evolutionary relationship within the NA family proteins. The search for correlated mutations shows several potentially important correlated positions that were not reported previously to be significant. The use of such an approach can be potentially important and gives new information regarding NA proteins of influenza A virus.