The incident took place at around 11pm last night at a property in Grimesthorpe Road South, Grimesthorpe.
A friend of the victim is understood to have reported the incident to the police anonymously via a phone booth located at the junction of Myrtle Road and Anns Road in Heeley. The man did not provide any information on the victim's identity.
A South Yorkshire Police spokesman said the two men are understood to have arranged to meet for a date after chatting on social media, but when the victim of the crime met the man he robbed him at knifepoint, stealing Â£40 in cash from him.
He added: "The victim believed he was meeting a gay man for a date, but it's now believed it was a targeting of the gay community in Sheffield."
The spokesman confirmed other incidents of a similar nature are being investigated in Sheffield.
The alleged offender was arrested yesterday, and was put into police custody. He is understood to have been accused of other violent offences.
Police are urging the victim, and anyone with information on the incident to come forward.
Anyone with information is asked to call South Yorkshire Police on 101, quoting incident 691 of 18/11/17, or to contact Crimestoppers anonymously on 0800 555111.