Officers are now appealing for witnesses after the incidents on Tuesday evening.
At around 9.15pm on Tuesday (9/2), a 29-year-old man was walking along the High Street in Aylesbury when he was approached by two men who started a conversation with him.
After a couple of minutes, one of them then snatched a £10 note from his hand while the other took the remaining £5.
Less than 15 minutes later, at around 9.30pm, the suspects then approached two boys riding their bikes on Station Way West.
They forced the boys – aged 15 and 16 – to give them their bikes and rode away from the scene. Both bikes have since been recovered.
Two teenagers, aged 16 and 17, from Aylesbury, have been arrested in connection with the offences and released on bail.
Investigating officer Detective Constable Paice O’Brien, from Aylesbury Priority Crime Team, said: “Both of these robberies left the victims shaken and our investigation into the circumstances of each incident remains ongoing.
“Although we have already made two arrests, we are appealing for anyone who may have seen either robbery to contact us on 101 with reference number 43210056364.
“We would also ask anyone in the area who might have CCTV that could have captured the incidents or the moments leading up to them to get in touch.”
Information can also be provided to Crimestoppers completely anonymously on 0800 555 111.