Baker was born in 1961 in Kaiapoi, New Zealand. Upon the suggestion by her mother Mary, Baker began running competitively at age 15 and showed ability right from the start. "I remember the first day Erin competed in a cross-country race. I was waiting for her to come in thinking God, she won't be very pleased because she hasn’t done very well. In fact, I missed her crossing the finish line a quarter of an hour earlier, in first place."
Baker is one of eight children. Her siblings include Phillipa Baker (New Zealand rower and 1991 Halberg award winner) and Kathy and Maureen who were both national titleists in swimming and aerobics.
Baker was originally coached by John Hellemans but controlled and developed her successful career by self-training, “I was self-trained. I just trained as much as my body would handle, and that was a shit load. I trained and trained, and I trained more if I had time. I never got injured so I would often do more in case somebody else was training while I was resting”.
In 1981 she was convicted of throwing explosive devices while protesting during the South African Rugby team tour of New Zealand. This act prevented her from entering the United States for several years, restricting her from competing in any American competitions. Baker was also known for her protests at the Hawaii Ironman competitions when she rebelled against the notion of the winner of the men’s division receiving a car and the women’s division winner receiving nothing for her efforts. She voiced her opinions on numerous occasions and as a result was well known as a controversial athlete.
She finished her triathlon career in 1994 with a record of 104 wins from 121 triathlons entered.
Baker was named “Triathlete of the decade” by American magazine Triathlete. The magazine commented on her success by saying, “We’ve stopped trying to figure Erin out, we just accept her as the best female triathlete that ever lived”.