Wyer will work closely with account executive Rachel Shepherd on the EDF Energy account at the London-based agency.
Trip Advisor projects – which number around 10 events each year - will also be among work for Wyer, who joined Live Union last week.
Live Union strategic director Jez Paxman said: "We’re really excited about Alexandra joining the agency. 2012 has seen rapid growth at Live Union and Alexandra’s appointment will ensure we continue to offer our clients an excellent service."
Wyer has 12 years event agency experience working with clients such as Astra Zeneca, BG Group, Canon and Pru Health.
Agencies she has worked for include Technovation, Pegasus, Involve and TBWA Hakuhodo.