The firm announced its gross inflows were up by 15% to £965m and it achieved an 85% increase in operating profit to £1m.
Assets under administration increased 32% to £7bn and turnover increased to £11.1m, an increase of 26%.
Nucleus' record performance came as the platform undertook its biggest ever technology upgrade – a move designed to deliver significant performance improvements for advisers.
The company said this would put it as the front of the "platform technology race".
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David Ferguson, chief executive, said: "Last year's financial performance was our best ever and so far this year we are substantially outstripping this.
"Not only have we seen record growth in H1 but H2 is off to a great start with July being our best ever month for inflows.
"Our numbers are evidence that a collaboration between like-minded advisers can have a real and sustainable impact and I remain hugely excited by the future possibilities for the business."
He admitted that the tech upgrade had come with "some inevitable issues" but he expects to overcome these quickly.
He said: "Our new technology represents a major milestone for us and paves the way for rapid future enhancement in key areas such as usability, connectivity and service automation.
"Importantly, our latest financial results mean that we can invest even more in proposition and technology upgrades from a very strong financial
base."
He said platform due diligence was more important than ever and added it was "a pivotal time" for Nucleus.