Here we sequenced and characterized the complete plastome of Bactris riparia, a species closely related to B. gasipaes and widely distributed in Western Amazonia. We performed a comparative genomic analysis with B. riparia and the other four Bactridinae species retrieved from GenBank. The plastome of B. riparia was 156,715 bp with a quadripartite structure. Gene content included 86 protein-coding genes (CDS), 38 tRNAs, and 8 rRNAs. Bactris riparia has 69 more base pairs than B. gasipaes, with identical numbers in IR, and more in LSC and SSC. The comparative analysis indicated that structure, collinearity, and IR/SSC borders of plastomes within subtribe Bactridinae are, in general, conserved. We predicted 69 SSRs in B. riparia plastome. Among them, ~80% consisted of A/T homopolymers. Among the 52 variable CDS, rbcL showed the highest non-synonymous rate, while the rps15 gene had the highest synonymous rate. Three genes (ccsA, cemA, and rpoC1) presented evidence of positive selection and 22 genes showed evidence of purifying selection. The phylogenetic tree based on plastome sequences set Bactris as more closely related to Astrocaryum than to Acrocomia. These new plastome data of B. riparia will contribute to studies about the diversity, evolutionary history, and conservation of palms.