Kuczynski's approval rating fell to 34 percent in July from 39 percent in June, while his disapproval rating rose to 58 percent from 51 percent last month, the monthly poll conducted by Ipsos Peru and published in local newspaper El Comercio showed.
In late June, Congress - dominated by defeated right-wing presidential candidate Keiko Fujimori's Popular Force party - forced Economy Minister Alberto Thorne to resign over allegations he improperly interfered in an airport contract, dealing a blow to Kuczynski's business-friendly administration. Thorne has denied any wrongdoing.
'The fall in popular support for [Kuczynski] could have many reasons, among them Alfredo Thorne's exit from the economy ministry,' Ipsos Peru President Alfredo Torres said.
Kuczynski, a former Wall Street banker who took office almost one year ago, has seen his approval rating decline from a peak of 63 percent in September amid a graft probe related to Brazilian builder Odebrecht and concerns over the airport contract.
Last week, Kuczynski met with Fujimori - the daughter of jailed former President Alberto Fujimori - to try to smooth over differences. Some 72 percent of respondents thought the meeting between the two leaders was positive for the country.
The poll of 1,280 Peruvians was conducted between July 12 and July 14 and had a margin of error of 2.7 percentage points.