Uganda is hosting more than a million refugees, nearly 700,000 of whom escaped the brutal civil war raging in neighbouring South Sudan since December 2013.
US ambassador Deborah Malac praised Uganda's "very progressive policy" towards refugees.
"We applaud that the government is committed to keeping the door open to refugees," she told reporters.
The $25.2 million (24 million euros) will be used to improve water and sanitation in refugee camps, fight gender-based violence and ensure ongoing protection.
Malac called for other countries to "step up and provide support" for the UN refugee agency and refugee-hosting countries.
Saying that there appeared to be "no end in sight" to the violence in South Sudan, Malac urged "more of a response from the international community, not just from the usual actors."
The UN says more than 52,000 South Sudanese refugees have been arrived in Uganda since the start of the year and the numbers are currently growing by over 4,000 per day.
The Ugandan minister for refugees, Hilary Onek, said the the scale of arrivals is stretching the capacity of one of the world's poorest countries.
"We are worried about the load we are bearing," Onek said. "It's getting a little heavy for us to manage."
Uganda has been praised for offering one of the most favourable refugee protection environments in the world -- providing for freedom of movement, the right to work and land for refugee camps.
However, there have been isolated incidents of local politicians rallying people against refugees.
In the past week police and residents near Nakivale refugee camp in the southwest of Uganda clashed in a dispute over land allocation to refugees.
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