The 'Diamonds' singer posted the picture via Instagram and accompanied it with the caption: "Dis n**ga....... #BartObsessed".
The former couple have been the subject of speculation regarding a reunion in recent months.
They have collaborated on songs and appeared to share a kiss at this year's VMAs.
Rihanna and Brown were also rumoured to have spent Thanksgiving together.
According to reports, when Rihanna finished her '777' tour she flew to Berlin on Thursday (November 22) to watch Brown perform at the O2 World Berlin concert venue.
Watch Rihanna's music video for latest single 'Diamonds' below: