Lieutenant Patrick Gisore Kabongo was murdered in the eastern city of Goma on November 9, in "an apparent case of ethnic hatred," the rights group said.
The 42-year-old soldier was an ethnic Tutsi from South Kivu province, accused by a crowd of being a member of the M23 rebel group because of his physical traits, according to HRW.
The M23 is a Tutsi-led rebel group that has captured swathes of territory in DRC’s eastern regions since launching an offensive in late 2021.
The group is backed by neighboring Rwanda, according to several western governments including the United States, as well as independent United Nations experts. Kigali denies the claim.
"Many people in Congo view the Tutsi community as supporters of M23, an abusive Rwanda-backed rebel group that resurfaced in late 2021," HRW said.
The rights group also said it had received "credible reports" that dozens of Tutsis were arbitrarily arrested by authorities in the Central African nation over the past year, accusing them of collaborating with the M23.
Government spokesman Patrick Muyaya condemned the murder of Kabongo on November 11, saying he had been killed because of his physical features. The Congolese army added that it regretted the death.
But HRW's senior DRC researcher Thomas Fessy said public condemnation alone will not prevent future hate crimes.
"The Congolese authorities should take serious steps to effectively address violence and intimidation that are rooted in hate and discrimination," he said.
HRW urged the Kinshasa government to ensure all those who are involved in ethnic violence are held accountable.