With the aim of developing an understanding of diameter growth variation in miombo tree species, this study examines the diameter growth of 53 selected trees from twelve (12) species using dendrometer bands in Kitulang’alo Forest Reserve, Morogoro Tanzania. The selected tree species included Julbernardia globiflora, Brachystergia boehmii, Combretum molle, Dalbergia melanoxylon, Pterocarpus species, Pteliopsis myritifolius, Xeroderris stulhumanii, Diospyros kirkii and Acacia nigrescens, Acacia senegal, Acacia robusta and other Acacia species. The study was done from July 2007 to December 2010. The study complements dendrometer band growth increment data by caliper based method to allow comparison of the two methods in measuring diameter growth. The study revealed that diameter growth rates vary significantly between and within tree species, and also in relation to age, season and microclimatic conditions of the forest. When fitted to nonlinear growth models, parameters were found to be significant Julbernardia globiflora, Brachystergia boehmii and all Acacia species. while non-significant to the rest of the studied species (P>0.05). The study also, found no significant difference between the dendrometer band and the calliper method in measuring diameter increment. However, the band dendrometer method is recommended for short term diameter increment studies (daily to monthly fluctuations) while the calliper method is suitable for long term monitoring of diameter increment studies. The use of high quality dendrometer bands is ideal for quality diameter increment data.