The aim of this study was to observe the influence of diazotroph inoculation on growth of paddy plants under greenhouse conditions. Diazotroph are the most studied and well known Plant Growth-Promoting Rhizobacteria (PGPR) that are able to promote plant growth via Biological Nitrogen Fixation (BNF) and phytohormone production. A total of four diazotrophic bacteria inocula were used for the experiment which include Azospirillum brasilense (Sp7), Herbaspirillum seropedicae (Z78), Enterobacter sp. (L2) and Gluconacetobacter sp. (L15). All four strains were able to fix nitrogen with the same ability but produces phytohormone indole-3-acetic acid (IAA) in different concentration. The inoculation effects were tested on paddy plants (Oryza sativa) variety MR220. The rice seedlings were planted in non-sterilized soil and grown under aerobic conditions. Growth of the host plants was measured on parameters such as plants dry weight, plants height, root elongation and total leaf chlorophyll and protein content. Results showed that following inoculation, overall plant growth observation for plants inoculated with L2 and Control positive (+100% N fertilizer) showed better plant growth compared to plants inoculated with L15, Sp7, Z78 and Control negative (+Sp7K). Plants inoculated with Sp7 and Z78 both showed inferior growth compared to Control negative due to excess amount IAA supplied by the inoculants that suppresses the plant growth. Results also showed promising effect of L2 inoculants, to promote rice growth through optimal phtyhormone (IAA) production activity plus the added benefit through successful fixed nitrogen intake by the plant that was provided by L2 via BNF.