Due to its strong digital sales,[7] "Radar" had a brief appearance on several U.S. Billboard component charts on the week the album Blackout debuted on the Billboard 200. The song peaked at number sixty-eight on the Billboard Pop 100[8] as well as on number fifty-two on the Billboard Hot Digital Songs.[7]

"Radar" also charted on the Billboard Bubbling Under Hot 100 Singles chart at number seven.The track received mostly positive reviews as a whole. Blender gave the track a positive review, stating it has a hook "most pop stars would kill for."[3] Stephen Thomas Erlewine of All Music Guide called it "relentless," and was chosen as one of the album's highlights.[4] Digital Spy commented that Radar is “A rave-tinged electro blipathon on which Spears is vocodered to the point of sounding extraterrestrial[5] whereas The Guardian criticised the song, saying it was "bending over backwards to annoy the listener."

The song is rhythmically and lyrically similar to Spears's Grammy Award-winning single "Toxic". Both of which incorporate influences of electropop, synthpop, and dance. In MTV's review of Blackout, "Radar" was described as

...an electro/Eurodisco approach, but keeps Spears' vocals more in the foreground. Instead of emulating a video game, she's accompanied sparingly by sonar pulses and distorted synths to keep the sound dangerous, because she's on the prowl. 'I got my eye on you.' she speaks at one point. 'And I can't let you get away'.