The 22-times grand slam singles champion announced her engagement on Thursday to Alexis Ohanian, co-founder of the social media company Reddit, who accompanied her to New Zealand for the ASB Classic which starts on Thursday.
American Williams, 35, is top seed for the tournament, a warm-up event for the Australian Open grand slam later in January, and she was whisked through a crowded airport, telling reporters she was excited to be in New Zealand for the first time.
"It's fun to go to new places," the world number two said.
Serena's older sister Venus is also competing in Auckland, an event she won in 2015, and said she was delighted to hear about her sibling's engagement.
Serena said it was unlikely the duo, who have won 14 grand slam doubles titles together, would team up to play in New Zealand.
"Probably not. I wish, we will see," Serena said.