The European Union, Tanzania's biggest development partner, and the World Bank have recently taken measures to sanction repressive policies.
Magufuli's reputation was boosted when he battled corruption after winning election in 2015.
But accusations of repression are growing and donors and former allies are increasingly frustrated at what they say are moves that stifle dissent and create obstacles for journalists and rights activists.
"The European Union and some of its member countries, as well as the United States, have repeatedly drawn the attention of the government to the human rights situation," said a European diplomat in Dar es Salaam on condition of anonymity.
"Even so, the situation continues to deteriorate, so we have had to move up a gear."
In October, the governor of Dar es Salaam, Paul Makonda, vowed to track down people suspected of engaging in homosexuality -- which is illegal in Tanzania.
In November, the EU said it would thoroughly review its financial support -- more than $100 million (88 million euros) a year -- in response to moves that undermined human rights and the rule of law.
Aid as political pressure
The EU, which also recalled its ambassador, said it was worried by "a shrinking of public space in Tanzania through the tightening of restrictions on the activities of civil society organisations, the media and many political parties."
Washington accused the Tanzanian government of fostering "an atmosphere of violence, intimidation and discrimination."
The EU's decision to reconsider its aid coincided with one by the World Bank to freeze a $300 million (265 million euro) loan for girls' education in protest against a move to expel pregnant girls from school and forbid them to continue their education after giving birth.
Meanwhile, Denmark announced the withdrawal of $10 million in aid owing to "unacceptable homophobic remarks".
In mid-December, four US senators called for the creation of a common front with "diplomatic partners" to put pressure on the Tanzanian government.
Magufuli has sought to shrug off the cuts, boasting that "Tanzania is on the right track".
The government also insisted that the anti-gay crackdown in Dar es Salaam was not official policy, but rather the "personal views" of the city's governor.
Many donors remain unconvinced however.
Magufuli, who says the diplomatic freeze is only with "those who do not want good to our country", has moved to flatter China.
"The Chinese are our friends, true long-time friends," he said recently while inaugurating a state-of-the-art library built with aid from Beijing.
Chinese funds are provided without conditions, he noted.
Poorest hit hardest
But observers say neither Magufuli nor donors want the situation to get any worse.
"It is possible that he (Magufuli) changes his course, that he shows flexibility if the pressure is maintained", suggested Jenerali Ulimwengu, an influential lawyer and a former Tanzanian diplomat.
"He cannot in any case rely only on the Chinese, who... cannot provide all the necessary help."
As for the European diplomat in Dar es Salaam, donors are well aware that cuts hit the poorest the hardest.
"But it is possible to send aid through other channels, including civil society organisations," the diplomat added.
"Bridges are not cut, discussions are underway and we hope that the Tanzanian government will eventually understand that development and respect for human rights must go together."
Others warn that using aid to influence government policy could do more harm than good.
"Suddenly halting or stopping aid can have dire unintended consequences for complex and important projects helping vulnerable people," wrote Irish senator Fintan Warfield, an openly gay LGBT activist, in response to calls for Dublin to review its support.
"It is only through continued support to the Tanzanian people and being a critical friend that we can hope to improve the human rights situation in Tanzania, and end the persecution of our LGBT+ brothers and sisters."