With flags flying at half-mast across the country, the Liberal Democratic Party that Abe had dominated for much of this century secured a win that gives Prime Minister Fumio Kishida the chance to cement his own power.
Three days after he was shot at an election rally, Abe's body was taken to Zojoji Temple in Tokyo for a wake on Monday evening, with a private funeral scheduled for Tuesday.
Authorities have raised questions about security after the killing of Japan's longest-serving prime minister, who served from 2006 to 2007 and from 2012 to 2020. He resigned in 2020 due to ill-health.
Unemployed man Tetsuya Yamagami, 41, is suspected to have approached Abe and opened fire during a campaign speech in the western Japan city of Nara on Friday.
Mr Yamagami has admitted to shooting Abe, Nara Nishi police said on Friday.
He was taken to the Nara District Prosecutor's Office on Sunday, and is being investigated as a “suspect for murder”, police said.
The Japanese head of the Unification Church said on Monday the suspect's mother had been one of its followers.
Kyodo news agency said Mr Yamagami believed Abe had promoted a religious group to which Mr Yamagami's mother made a “huge donation”.
He told police his mother went bankrupt from the donation, the Yomiuri Shimbun newspaper and other media have reported.
Mr Yamagami was not a member of the church, said Tomihiro Tanaka, president of the Japan branch of Family Federation for World Peace and Unification ― known as the Unification Church.
Mr Yamagami's mother did not comment on whether she was a member.
In elections held on Sunday, the LDP and its ruling coalition partner extended their majority in the upper house of parliament. A majority was already in place in the lower house of the Diet.
But what would normally have been a time of celebration at LDP headquarters was a sombre affair.
A moment of silence for Abe was offered in his memory, and Mr Kishida's face remained grim as he pinned rosettes next to winning candidates' names on a board in a symbol of their victory.
US Secretary of State Antony Blinken met with Mr Kishida during a brief stopover on Monday to offer condolences on behalf of President Joe Biden.
“I shared with our Japanese colleagues the sense of loss, the sense of shock that we all feel — connected people feel — at this horrific tragedy,” Mr Blinken said.
“But mostly, I came at the president's behest because more than allies, we're friends. And when a friend is hurting, other friends show up.”
The LDP and its junior partner Komeito won 76 of the 125 seats contested in the chamber — up from 69 previously. The LDP won 63 seats, up from 55, to win a majority of the contested seats, though it fell short of a simple majority on its own.
With no elections set for another three years, Mr Kishida has breathing space to attempt to implement an ambitious agenda that includes expanding defence spending and revising Japan's pacifist constitution — a long-held dream of Abe.
Abe led the largest faction within the LDP. Some analysts said his death could lead to potential turmoil within the party that might challenge Mr Kishida's control.
Mr Kishida said he would take up the difficult problems that Abe was not able to resolve, such as revising the constitution. He said he hoped there could be discussions on the topic during the next session of parliament.
“We gained strength from voters for stable government of this nation,” he said.