The protesters marched to the health ministry, where they handed a letter to minister Ivo Garrido demanding better treatment and more privacy for patients with HIV, which affects 16 percent of adult Mozambicans.
Health authorities closed specialised HIV centres this year, blending treatment into the broader healthcare system, saying that the separate centres contributed to stigma surrounding the disease.
But activists say the closures were followed by a dramatic drop in patients seeking treatment.
HIV patients have special green health insurance cards that immediately reveal their status to other patients in general clinics, the activists argue.
"Due to the decision of closing the (day hospitals), there are more and more people who abandon the treatment; the number of deaths are increasing; the compliance to the treatment is decreasing; discrimination against people affected by HIV/Aids is dramatically increasing," march organisers said in a statement.
Christian Reed, a medical anthropologist studying HIV treatment in Mozambique, said the number of patients seeking treatment in Pemba, in the north, dropped from about 50 to three or four a day after the local day hospital closed.
"The ones who don't want their families to know are not coming," Reed said.
"Access to services is more difficult now," Reed added. "Where you used to have a hospital full of HIV specialists ... now everybody's mixed together."
Health authorities announced the closure of the day hospitals in February.
Non-governmental organisation workers say the move was also meant to free up a ratio of one doctor for every 23,000 people.