The Perfume singer, who flew to Louisiana with her boyfriend David Lucado and sons Sean, eight, and Jayden, seven, for Jamie Lynn's nuptials, was clearly thrilled to see her 22-year-old sister tie the knot with her fiancé Jamie Watson.
"Yesterday was magical :)," wrote Britney. "So happy I could be a part of my little sister’s big day. Congrats @jamielynnspears!!"
Britney and her two sons flew to Louisiana for Jamie Lynn's wedding
The morning after the wedding Britney was spotted leaving a hotel in New Orleans hotel with her son Jayden and five-year-old niece Maddie, who is Jamie-Lynn's daughter from her relationship with Casey Aldridge.
Jamie Lynn Spears marries Jamie Watson in Louisiana wedding ceremony
The 32-year-old scooped her brunette locks into a ponytail and sported a light purple jumper and black leggings as she and her mother Lynn took the youngsters to the cinema.
Newlywed Jamie Lynn sporting a garter on her leg
According to E! Britney wore a form fitting grey gown with a bejewelled neckline for her sister's wedding, while the bride sported an ivory lace gown by Liancarlo and swept her hair into an elegant low bun.
Jamie Lynn has yet to comment on her wedding but posted a picture of herself wearing a garter on her leg the day after the ceremony took place.
While the wedding was a private affair, sources confirmed to E! that it took place in the tea room at Audubon Tea Room in New Orleans.
Jamie Lynn with Jamie Watson and her daughter Maddie
Despite keeping a low profile throughout her engagement, Jamie Lynn couldn't resist telling her Twitter followers when the search for her dream dress was over several months ago.
"Finally found my perfect dress at @idobridalcouture !!!!!" she posted along with a picture of herself, Lynn and Maddie clutching a bag from the Baton Rouge-based shop.
"Thank y'all so much for making me feel so special and being so accommodating!!!!"
22-year-old Jamie Lynn is a county singer
Aspiring country singer Jamie Lynn announced her engagement to Jamie in March 2013.
Britney Spears congratulates sister Jamie Lynn on her engagement
"Guesssss what??????," she tweeted at the time, alongside a photograph of her beautiful diamond engagement ring. "He did good," she later added.
The couple announced their engagement in March 2013
This will be the first marriage for Jamie Lynn. She was previously engaged to Casey, who is the father of her young daughter, but the couple split in 2010.
Britney Spears proud of little sister's country music debut as sisters set to sing duo
Britney meanwhile wed her childhood friend Jason Alexander for a marriage that lasted just 55 days, before tying the knot with dancer Kevin Federline in 2004. The couple, who are parents to Sean and Jayden, went their separate ways in 2007.