Headteacher, Mr Meilir Tomos, was joined by the children, staff and governors to welcome the guests, who also included Deputy Leader of Cardiff Council, and Cabinet Member for Education, Employment and Skills, Cllr Sarah Merry, local politicians, and those who played a key part in the school's construction.
The new school has been funded by Cardiff Council and Welsh Government, through the city's £164m, Band A 21st Century Schools and Education programme.
Primary Welsh-medium education provision in the local area has doubled, with the new school site able to accommodate up-to 420 pupils, across two classes per year, from reception class to year 6, as well as providing 80 part-time nursery places.
Ysgol Glan Morfa's gates opened for the first time at its new £7.8m home in September, after the school relocated from its former site on nearby Moorland Road over the summer.
Reflecting on the school's journey, Mr Tomos said: "I am delighted that Ysgol Glan Morfa is now officially opened. This building represents a new and an exciting era for the school as it enables us to offer our children even more educational opportunities, in a state-of-the-art and purpose built building.
"I would like to thank our fantastic community for embracing and supporting Welsh-medium education and ensuring that the Welsh language is thriving in this part of the city. It also moves us a step closer to realising our ambition to be one of the best schools in Cardiff and in Wales."
Leader of Cardiff Council, Cllr Huw Thomas, said: "This is another significant moment for Welsh-medium education, not just for Splott, but for the whole of Cardiff. Officially opening Ysgol Glan Morfa is part of our continuing commitment to encourage the growth of the Welsh language in the capital city.
"Doubling provision in Splott is a further example of the work we are doing as a council, in partnership with Welsh Government, to meet the increasing demand for Welsh-medium education in Cardiff, through our multi-million pound 21stCentury Schools programme.
"I am delighted to have shared in the enjoyment of the occasion with all the children, Mr Tomos, and the whole school community. I want to thank Meilir and Chair of Governors, Gareth Price, along with everyone involved with the project, for the work they have put in to ensuring a smooth transition to the new site.
"I look forward to seeing what the future brings for Ysgol Glan Morfa, as it enters a new era, in a new home, fit for the 21stCentury."
Kirsty Williams said: "Our 21st Century Schools Programme is the most ambitious school building programme since the 1960s and will see an overall investment of £1.4billion. This is worth every penny because our pupils deserve the absolute best learning environment for their development and I'm so pleased Ysgol Glan Morfa delivers this. I would like to thank everyone involved, and wish Mr Thomas, his staff and pupils the very best of luck for their future in this new school."
The scheme has created approximately 2,500 square metres of floor space, in a two storey primary school and nursery building.
The new school also incorporates facilities available for use by the wider local community in Splott, including a multi-use games area and a room available for hire.
Deputy Leader of Cardiff Council, and Cabinet Member for Education, Employment and Skills, Cllr Sarah Merry, said: "The new Ysgol Glan Morfa is further evidence of what we are doing to continue the expansion of Welsh-medium provision and widen parental choice in Cardiff. The Capital Ambition, and Cardiff 2020, our vision for education and learning in Cardiff, makes a clear commitment to provide more school places, ensuring that provision is available to all families who choose a Welsh-medium education."
Cardiff Council and Welsh Government announced its next phase, or Band B, of the 21stCentury Schools and Education programme at the end of last year, totalling £284m.
Cllr Sarah Merry, added: "The £284m Band B investment in our schools is the biggest Cardiff has ever seen. It will allow us to increase the momentum we have established through the exciting range of new schools we have delivered with Welsh Government over recent years under Band A, and continue to create inspiring, sustainable, community-focussed schools, in which all children and young people can achieve their potential."