Tributes began pouring in from countrywide dignitaries.
In 1963 she founded the Marie Adelaide Leprosy Centre in Karachi, Pakistan's first hospital dedicated to treating the disease, and opened branches across the country. Following the news of her demise, condolences poured in for the late humanitarian on social media.
Not required to take the veil or live in seclusion, she ended up in Pakistan by chance.
Dr Pfau, the founder of the National Leprosy Control Programme in Pakistan, was in charge of the Marie Adelaide Society of Pakistan (MASP), where leprosy patients are treated.
She was awarded Hilal-i-Imtiaz, second highest civilian award of country in 1979, and later granted Pakistani citizenship in 1988.
Dr Pfau had been hospitalized at a private hospital in Karachi for two weeks due to age-related illnesses, where her condition had been worsening.
Born in Leipzig, Germany on September 9, 1929, Dr Pfau devoted the last 50 years of life to fighting leprosy in Pakistan. "We owe u a debt of gratitude Dr Ruth Pfau". Her spirit of selfless dedication leaves a void that will be hard to fill.
In 1996, the World Health Organization declared that leprosy had been controlled in Pakistan, which led Pfau to the more challenging task of eliminating the disease. Today she went home to her Maker.
The Prime Minister, in his message, said she came to Pakistan at the dawn of a young nation looking to make lives better for those afflicted by the disease. "We owe u [you] a debt of gratitude Dr. Ruth Pfau". She was only 29 when she came to the nation.
Many Pakistanis said they would like to see their government give Pfau a state funeral because of her services to the country. She was admitted to the Agha Khan Hospital on Wednesday where she lost her life at 87 years old.
"Pfau may have been born in Germany, her heart was always in Pakistan", Prime Minister Shahid Khaqan Abbasi said in a statement.