The National Party of Scotland (NPS) was formed in 1928 after John MacCormick of the Glasgow University Scottish Nationalist Association (GUSNA) called a meeting of all those favouring the establishment of a party favouring Scottish independence. The meeting was presided over by Robert Cunninghame-Graham, who had been a Liberal Party, then Labour Party politician. The NPS was formed by the amalgamation of GUSNA with the Scots National League, Lewis Spence's Scots National Movement and the Scottish Home Rule Movement. Lewis Spence was the first nationalist to stand for election in 1929. He contested Midlothian and Peebleshire Northern and came fourth, with 4.5% of the vote.

The NPS contested many elections in its short existence but never managed to get any of its candidates elected to parliament. In 1932 a home rule organisation the Scottish Party was formed by former members of the Conservative Party. MacCormick desired unity between the Scottish Nationalist movement and made contact with the Scottish Party. Increasingly the two parties began to co-operate, and when the Scottish Party chose to contest the Kilmarnock by-election in November 1933 the NPS endorsed their candidate. In 1934 the NPS and Scottish Party merged to form the Scottish National Party.

The NPS was a left-of-centre party, favouring independence for Scotland. The celebrated poet, Hugh MacDiarmid was a member, but was expelled on account of his Communistic beliefs (ironically he would later be expelled from the Communist Party of Great Britain for his Scottish Nationalist beliefs).

There was another National Party of Scotland formed in the 1950s as a breakaway from the SNP. This small party did not last long and had a small membership and was formed by expelled members of the SNP who had been involved with the 55 Group.