Heather Phares from AllMusic wrote that "Teleman's sharpened songwriting allows the haunting moods beneath the cheery melodies to cut more deeply, with odd yet potent motifs (glue, shoes, flickering lights) guiding their meditations on permanence and impermanence".

Billy Hamilton of Under the Radar praised the album, stating, "By simply placing a fuller smile over their songwriting, Teleman have created a sharp, smart pop record that—if there's any justice in this world—should bring them the wider attention they merit".

The Guardian's Michael Hann quoted that the album was "proof of the desirability of letting musicians develop", noting the progression made from three band members' previous group Pete and the Pirates.

Sofie Jenkinson of The Line of Best Fit wrote that "As a whole Brilliant Sanity is as fresh as it is reminiscent, as catchy as it is challenging and thoughtful – a welcome nod to what has been, with a firm eye on the horizon".

In a mixed review, Juan Rodríguez of No Ripcord said, "Brilliant Sanity does adequately describe their modish, classy new wave approach, though— there's a zany kookiness to their Todd Rundgren-inspired cosmic pop that sells the London band short, as they wouldn't even dare to veer off from their studiously structured compositions".