Euglenids represent a group of protists with diverse modes of feeding. To date, only a partial genomic sequence of Euglena gracilis and transcriptomes of several phototrophic and secondarily osmotrophic species are available, while primarily heterotrophic euglenids are seriously undersampled. In this work, we begin to fill this gap by presenting genomic and transcriptomic drafts of a primary osmotroph, Rhabdomonas costata. The current genomic assembly length of 100 Mbp is 14× smaller than that of E. gracilis. Despite being too fragmented for comprehensive gene prediction, comparison of the transcriptomic and genomic data revealed features of its introns, including several candidates for nonconventional introns. 16 % of transcripts bear a recognizable partial splice leader sequence. A set of 39,585 putative R. costata proteins were predicted from the transcriptome. Annotation of the mitochondrial core metabolism provides the first data on the facultatively anaerobic mitochondrion of R. costata, which in most respects resembles the mitochondrion of E. gracilis with certain level of streamlining. R. costata synthesises heme by a mitochondrial-cytoplasmatic C4 pathway with enzymes orthologous to those found in E. gracilis. The low percentage of green algae-affiliated genes, supports the ancestrally osmotrophic status of this species.