The former charity worker will replace long-standing MEP Richard Howitt, who stepped down earlier this month.
The Labour Party has chosen its new Member of the European Parliament for the East of England.
Alex Mayer will replace Richard Howitt, who stood down after 22 years as an MEP earlier this month.
Ms Mayer previously worked for the British Heart Foundation as its fundraising manager for Norfolk, and has managed Cambridge Labour MP Daniel Zeichner's parliamentary office since he was elected in 2015.
She said: 'It is a huge honour and privilege to become Labour MEP for the Eastern Region.
'After the tremendous disappointment of the Brexit vote, in many ways this is a strange time to be entering the European Parliament. However there is an important job to be done. As your MEP, I will stand up for progressive values, I will work to get the best deal we can for the East of England, particularly when it comes to protecting jobs, the economy and living standards in our region.
'I pay tribute to my friend and colleague Richard Howitt who I am replacing. l know I have big shoes to fill.'
First elected in 1994, Mr Howitt served on various committees in the European Parliament, dealing with human rights, foreign affairs and defence policy.
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