Lim Cheng Hoe, 61, the former head of protocol at the Ministry of Foreign Affairs, was sentenced to 15 months in jail for inflating expenses for thousands of dollars' worth of pineapple tarts and wine bought as gifts for dignitaries.
In a separate case, Edwin Yeo Seow Hiong, 40, an assistant director at the Corrupt Practices Investigation Bureau, was sentenced to ten years in jail for misappropriating Sg$1.76 million ($1.4 million) worth of government funds.
The two men had earlier pleaded guilty.
Several corruption scandals prompted the government last year to introduce new rules in the civil service to further deter graft.
"This case has caused public disquiet as it involved a high-ranking public officer who deceitfully obtained public funds by virtue of his position and the trust reposed in him," district court Judge Eddy Tham said in a written judgement in the case involving senior diplomat Lim.
State prosecutors had initially slapped Lim with 60 charges of overbilling the government for gifts bought for foreign officials during overseas visits, totalling Sg$88,997 (US$70,280).
Lim headed the foreign ministry department responsible for organising ministerial and presidential trips overseas.
According to charge sheets, Lim claimed for more than 10,000 boxes of pineapple tarts, a savoury popular in Singapore, but only 2,200 were used as gifts.
Lim asked vendors for blank receipts and overstated the number of boxes purchased. He also claimed for 248 bottles of wine but only bought 89.
In Yeo's case the judge said the decade-long prison sentence was necessary since he was a law enforcement officer and the court had to "signal the society's moral opprobrium over his offences and deter any like-minded offenders".
Yeo had used the government funds he misappropriated to gamble at a casino.
Last year Peter Lim, the former head of the civil defence force, was jailed for six months for receiving oral sex from a female executive of a defence supplier in return for favours.
Large-scale graft cases remain rare in Singapore, which pays its civil servants some of the world's highest salaries to deter corruption.
The city-state has been ranked by Transparency International and other watchdogs as among the least corrupt nations in the world.