The Downton Abbey star wore a stunning marigold Cushnie et Ochs frock when she attended the annual White House Correspondents' Dinner in Washington, D.C., on Saturday.
The actress shared a cheerful photo on Instagram ahead of the annual "nerd prom," writing, "Headed to#nerdprom2016 #whcd #joy."
Dineen passed away earlier this year while Dockery was in the middle of an American press push for the final season of her hit period drama.
"I was honored to know John, to love him and be loved by him," Dockery said at Dineen's funeral in Ireland back in December. "He was my friend, my king, my hero, my everything. We celebrate him, we honor him and we will miss him."
Dockery has largely stepped out the public eye following Dineen's death, but she has slowly begun to return to her normal routine in recent months. In March, the British actress was spotted back on the set of her TNT drama, Good Behavior, in North Carolina.
The actress is hardly the only big star at the WHCD. Other guests include models Kendall Jenner and Ashley Graham as well as Scandal star Kerry Washington and actress-turned-activist Emma Watson.