Erin Anne Blanchfield was born and raised in Elmwood Park, New Jersey. Blanchfield began training Brazilian jiu jitsu at age seven and is now a black belt in that discipline. Began competing in kickboxing and grappling tournaments at age nine and by age twelve decided that she wanted to be a professional fighter. She was inspired in part by watching women's pioneers Ronda Rousey and Miesha Tate fight in Strikeforce. Blanchfield got her nickname "Cold Blooded" from her father due to her calm demeanor and poker face during fights. She told Ariel Helwani on the MMA Hour that she wants to be an MMA comentator after her fighting career is over.

At 18 Blanchfield competed at EBI 12 and won a Flyweight grappling title. One year later she made her MMA debut at Cage Fury FC 70, where she defeated Whitney Pyles by first round TKO. She then moved to Invicta FC where she defeated Brittney Cloudy (Invicta FC 30) and Kay Hansen by majority decision (Invicta FC 32). Blanchfield then faced fellow future UFC Flyweight Tracy Cortez at Invicta FC 34. Despite threatening with an armbar for most of the first round and dominating the grappling exchanges in the third round Blanchfield lost the fight via split decision. 

Blanchfield hasn't lost since in her MMA career. She defeated Gabriella Gulfin via americana (Cage Fury FC 76), Victoria Leonardo via KO (Invicta FC 39)(Performance of the Night), and future The Ultimate Fighter runner-up Brogan Walker-Sanchez via unanimous decision (Invicta FC 41)(Performance of the Night) in order to win a UFC contract.

Blanchfield made her UFC debut against Sarah Alpar (UFC Fight Night: Smith vs. Spann). She won via unanimous decision and dominating the fight to such a degree that the judges scored it 30-26, 30-25, 30-25. She then defeated fellow highly-touted prospect Miranda Maverick via unanimous decision (UFC 269). Most recently, she defeated JJ Aldrich via guillotine choke in the second round (UFC UFC Fight Night: Volkov vs. Rozenstruik).