The Nikkei 225 index rose 0.18 percent, or 42.25 points, to close at 24,083.51, the highest since early October in 2018. The broader Topix index was up 0.50 percent, or 8.72 points, at 1,744.16.
Tokyo shares opened higher as bullish US stocks were driving Tokyo's strength, dealers said.
"Market sentiment remained positive for the rest of the day thanks to strong US shares," said Toshikazu Horiuchi, a broker at IwaiCosmo Securities.
Wall Street stocks again finished at records on Friday on the back of a US-China trade deal signed last week, robust US economic data and mostly solid corporate earnings.
The trade agreement was skewed in favour of Washington, noted Masayuki Kubota, chief market strategist at Rakuten Securities, spawning speculation that China might not be able to keep its promises.
The next stage of US-China trade talks will be tougher as Beijing is unlikely to budge further, he said.
"Nonetheless, the flawed 'phase-one agreement' is a fair wind for the global economy over a short period," Kubota added.
"We believe stock prices will continue to be higher globally in the first half of 2020 with easing in US-China tensions leading to expectations for a recovery in the world economy."
The dollar held steady, trading at 110.19 yen against 110.12 yen in New York on Friday afternoon.
"The weak yen also helped encourage investors to buy," Horiuchi told AFP.
The Bank of Japan starts a two-day policy meeting Monday but is widely expected to stand pat.
In individual stocks trade, ANA Holdings rose 0.43 percent to 3,656 yen after the Nikkei business daily reported All Nippon Airways is entering a comprehensive tie-up with Singapore Airlines to fend off competition in an increasingly crowded Southeast Asian market.
Sony was up 0.84 percent at 7,991 yen while Toshiba dropped 3.53 percent to 3,815 yen after the company reported that a subsidiary padded sales by 20 billion yen ($181 million).