After the victory of the Avengers over HYDRA, Helen Cho was summoned by Tony Stark to attend the wounds of Clint Barton, who was severely wounded during the battle. While Cho healed Barton, Bruce Banner was surprised how the machine created tissues, which she replied that this was the future and that soon they would no longer need Stark's armors to save the world. Stark arrived and told her that that was the plan, besides he invited her to a party, to which she agreed to attend only because Thor was going to attend the party.
She eventually attended the party and stayed to the end of this and witnessed how the Avengers challenged each other to lift Mjolnir. As they all failed in the attempt, Thor told them that none was worthy of carrying his magical hammer. Suddenly, Ultron burst into the party and attacked them by Iron Legionnaires. When Cho was about to be attacked by a Legionnaire, Ultron ordered the drone not to attack her, as he was interested in her technology. The next day, she and her friends discussed the events of the night before. Cho was surprised and asked Stark why his own invention would want them dead.
Days later, Ultron and his sentries broke into her laboratory and ordered her to build a new body for him. As she did not want to cooperate with him, a sentry used Loki's scepter to take control over her. Under Ultron's control, Cho built the new body, and also she was surprised at how her cradle and the Vibranium particles were consistent with each other. Ultron then revealed to her that the gem was actually an infinity stone. Eventually, she was released from the mind control by Wanda Maximoff, who found out Ultron's true intentions. Ultron attacks her after she disconnects Ultron's mind and the synthetic body. When Captain America arrived, she advises him not to destroy the new body as the gem on his forehead was too powerful.
After Ultron's defeat, Helen Cho was seen working at the New Avengers Facility, the new headquarters of the Avengers.
- In the comics, Helen Cho is the mother of Amadeus Cho.