The de Soysas are famous for their philanthropic work of building a vast array of institutions across the country for social upliftment. The many schools, hospitals, churches, roads, reservoirs as well as the several temples, the literary projects and the promotion of indigenous arts & crafts, bare testimony to their broad vision.
In 1886 a facsimile of the Yapahuwa Gate was gifted to the Royal Institution by CH de Soysa to be displayed at the Victoria & Albert museum, London in order to raise awareness and appreciation of the ancient architectural tradition of the Island.
Charles Henry de Soysa initiated and sponsored the translation, printing and publication of the ancient Sanskrit text, Hitopadesha and works by the 6th century poets Kumāradāsa and Kālidāsa such as the Sanskrit Mahākākvya called the Jānakī-haraṇa, a work (believed to be of a Sinhala prince) that had been lost for nearly a millennium, but had barely survived in India. He supported the work of Ven. Ratmalane Sri Dharmarama Thero, the Chief Incumbent of the Vidyalankara Pirivena and the famous scholar monk and Buddhist revivalist, Ven. Weligama Sri Sumangala Mahanayake Thero, including the publication of the 3rd standard reader.
Though a Christian, Charles de Soysa maintained a convalescent home at his Alfred House estate for the Buddhist clergy. Jronis de Soysa was a prime benefactor towards the construction of the library of the Hanguranketha Temple. He established a Legal Aid Society, a library and an association for social reform (Sadarana Sarana Samagama) in Moratuwa. Jronis de Soysa also helped widen the scope for Mudaliyer appointments, recognition and social mobility which was previously reserved for government service.
Though several well known writers and politicians of the 20th century had commented that the 1848 Rebellion had leaders, but lacked leadership and a following comparable to 1818, it was Gate Mudaliyer Susew de Soysa who perhaps was the first to realize it first-hand and had advised Weera Puran Appu about the futility of the campaign. He was a witness to Puran Appu being treated as a king after he had been proclaimed as 'King'. The 'De Soysa Charithya' contains the oldest written account of Puran Appu's status elevation.
Charles Henry de Soysa promoted traditional arts, crafts and puppetry. He extend patronage to traditional theater when it was deemed to be unsuitable for upper-class society. In 1870 the nādagama was performed at Alfred House in a week long festival for an audience that included the Duke of Edinburgh. Later, JSW de Soysa promoted nurthi productions of John de Silva and Don Bastian.
Circa 1875, when hundreds of farmers in the Walapane district were evicted for the non-payment of the grain tax, it was Charles de Soysa who gave land for resettlement of those displaced families and campaigned for the abolition of the paddy tax. Later, Sir James Peirs and George Wall were honourd by the Cobden Club, the famous association in the United Kingdom for their legislative role in the abolition of the tax.
The de Soysas were among the first to emphasize on Eastern dress among the elite of the early 20th century. They introduced the saree to high society events such as the Governor's Ball. In 1930, Lady Evelyn de Soysa, Marjorie de Mel (Perera Abhayawardena) and Loranee Senaratne were co-founders of the Lanka Mahila Samiti, the oldest women's organisation in Sri Lanka, which pioneered the establishment of women's societies in rural areas working for the progress of the rural women.
Ordained in 1934, Reverend Charles Harold Wilfred de Soysa became the first Ceylonese Bishop of Colombo in 1964. He gained international recognition for his role in the Ecumenical Movement and the Church Union.