Sorghum [Sorghum bicolor (L.) Moench] is one of the most important crops worldwide in terms of food, feed, and source of cellulose biomass. Genetic transformation of sorghum plants has been used in crop improvement and for functional analysis of genes isolated from the genome. However, it is extremely difficult to produce transgenic sorghum plants for these purposes. We present an improved genetic transformation method involving particle bombardment. The described transformation procedure led to three main advancements over current procedures, including: (1) Modification of M11 medium to optimize plant hormone content and concentration during callus induction from an immature embryo, callus growth, and regeneration of plantlets; (2) Isolation of two sorghum accessions with higher regeneration frequencies; (3) Optimization of physical parameters such as helium gas pressure, culture conditions on osmotic medium before bombardment, and others. Improved genetic transformation of sorghum calli by particle bombardment was achieved and regenerated sorghum plantlets were obtained. Genomic DNA from these sorghum plantlets was analyzed to confirm successful genetic transformation. This work was supported by Genomics for Agricultural Innovation from MAFF, Japan (GMZ1003).