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."
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.
Baker is one of eight children. Her siblings include Philippa Baker (New Zealand rower and 1991 Halberg award winner) and Kathy and Maureen who were both national titleists in swimming and aerobics.
In the 1993 New Year Honours, Baker was made a Member of the Order of the British Empire, for services as a Triathlete.
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".
