Phyllis Dewar had the following podium finishes at major championships: 1st in the 1934 British Empire Games 100 yards Freestyle, 1st in the 1934 British Empire Games 440 yards Freestyle, 1st in the 1934 British Empire Games 4×110 yards Freestyle Relay (with Irene Pirie and the non-Olympians Florence Humble and Margaret Hutton), 1st in the 1934 British Empire Games 3×110 yards Medley Relay (with the non-Olympians Margaret Hutton and Phyllis Haslam), 1st in the 1938 British Empire Games 4×110 yards Freestyle Relay (with Noel Oxenbury and the non-Olympians Dorothy Lyon and Mary Baggaley).
|1936 Summer||20||Berlin||Swimming||Women's 100 metres Freestyle||Canada||CAN||6 h1 r2/3|
|1936 Summer||20||Berlin||Swimming||Women's 4 × 100 metres Freestyle Relay||Canada||CAN||4T|
|1936 Summer||20||Berlin||Swimming||Canada||Semi-Finals||Heat One||6||1:09.6|
|1936 Summer||20||Berlin||Swimming||Canada||Round One||Heat One||4||QC||1:09.2|
|1936 Summer||20||Berlin||Swimming||Canada||CAN||Round One||Heat One||3||QU||4:49.7|