The former Suits star is giving up her current charitable commitments with the organisation to focus on her new life as a member of the royal family with a "clean slate".
Heartfelt congratulations to Meghan Markle (our ambassador for the past 2 years) on her engagement to Prince Harry! We're grateful for her support of the world's most vulnerable children. We wish the couple every happiness together. pic.twitter.com/xj8Q0AA5bd— World Vision (@WorldVision) November 27, 2017
World Vision's Lara Dewar, who travelled to India with Ms Markle earlier this year, thanked the actress for her support and praised her passion for improving children's lives and campaigning for girls' rights.
"Meghan is a true humanitarian," the chief marketing and development officer said.
"We're deeply grateful for her contribution as a global ambassador for World Vision over the past two years and for helping to raise awareness for the world's most vulnerable children.
"I personally witnessed Meghan's passion to improve the lives of children, and know her heart to advocate for the rights of girls - to hear and amplify their important voices.
"She will undoubtedly bring vast energy to her charity work as a member of the royal family.
"We can't wait to see what the future holds for her and Prince Harry - a couple who clearly have a heart for social justice."
Ms Markle will become a full time royal after marrying Prince Harry in May at St George's Chapel, Windsor Castle.
She will join the Royal Foundation of the Duke and Duchess of Cambridge and Prince Harry as its fourth patron.
Kensington Palace said on Tuesday that the American star would become a British citizen, and also would be focusing on her new life, rather than past charities.
Harry's communications secretary Jason Knauf said: "She has made the decision that she wants to start with a clean slate and focus on the UK, and getting to know this country, and travelling around the Commonwealth."