The Dutch striker’s three goals took her to 52 WSL goals, breaking the mark she previously shared with England and Lyon forward Nikita Parris.
Arsenal were three up inside 15 minutes through goals from Katie McCabe, Miedema and Caitlin Foord.
Miedema, who was making just her 50th Super League appearance, completed her hat-trick before half-time, and Foord added a sixth after the break to maintain the Gunners’ perfect start to the season.
Spurs, who also missed a penalty, had to wait until the 76th minute for a consolation, when Lucia Leon was on target. Summer signing Alex Morgan announced earlier in the day she was unavailable after suffering an injury setback.
Arsenal are now clear at the top of the WSL table after Everton’s 100 per cent record was ended by a 2-2 draw with Brighton.
Elsewhere, Christen Press scored her first Manchester United goal as Casey Stoney’s side beat West Ham 4-2 to continue their unbeaten start to the season.
Additional reporting by PA.