Helen Lyster Nicol was born on 29 May 1854 in Edinburgh, Scotland, the sixth of 10 surviving children of Margaret Cairns Smith and her husband, David Nicol, head gardener at the Orphan Hospital in Edinburgh. When Helen was two years old, the Nicol family left Scotland on the Strathmore and arrived at Port Chalmers, New Zealand, in October 1856. They were Free Church settlers and strict Sabbatarians, and Helen remained a staunch church member all her life. Her father worked as a gardener for two years for W. H. Reynolds and James Macandrew. He prospered and bought 200 acres of rural land and part of a block in central Dunedin. All this property he bequeathed to his unmarried daughters, Helen and Lavinia, who inherited it when he died in 1890.
Helen Nicol taught in the ragged Sunday school, and this experience made her familiar with the poverty and desertion which many women and children endured. Convinced that drink was the fundamental cause of all social evil, she became a lifetime abstainer and prohibitionist. She joined a number of temperance organisations; at various times she was a member of a Band of Hope, the Juvenile Temple, the Independent Order of Good Templars, the Blue Ribbon Army and the New Zealand Women's Christian Temperance Union (WCTU). Particularly concerned with children, under the auspices of the WCTU she set up the Loyal Temperance Legion, which provided vocational training.
Helen Nicol's zeal for temperance led her to work for the enfranchisement of women. Her aim was for women to elect 'men of good moral character' who would enact prohibition, thereby restoring purity to the home. She argued in favour of women's rights and pointed out the ways in which women were disadvantaged by the law, stating, 'We do not want a seat in Parliament, but we do want a vote to put the right kind of men there.'
Helen Nicol pioneered the suffrage campaign in Dunedin. She wrote letters to the press and, as superintendent of the franchise department of the Dunedin branch of the WCTU, corresponded with other suffrage leaders, most notably Kate Sheppard and Sir John Hall. The women of Otago returned the highest number of signatures to each suffrage petition. Such work took its toll. Helen Nicol wrote of the weariness she experienced, and Harriet Morison, first vice president and later secretary of the Tailoresses' Union of New Zealand, emphasised that her friend had stood up for suffrage 'when to declare one's self a woman's franchist was to bring down on your devoted head the ridicule of most of your friends'.
The suffrage campaign in Dunedin was especially bitter because of the vigorous drink lobby led by H. S. Fish, the city's member in the House of Representatives, where he headed the opposition to women's enfranchisement. In 1892 Fish organised a counter-petition to the pro-suffrage petition then being circulated. Confusion was such that Helen Nicol started yet another petition to enable those women who had signed in error, believing that Fish's petition was pro-suffrage, to protest.
In response to Fish's 'hostile attacks' Harriet Morison, assisted by Helen Nicol and other women, founded the Women's Franchise League in Dunedin in 1892. Its sole aim was to win the vote. It reached out to those beyond the temperance lobby and built on Morison's work for the tailoresses' union, tapping the support of the large number of young women working in the clothing establishments in Dunedin. Helen Nicol and Marion Hatton, the league's Dunedin president, held public meetings in rural townships in Otago and Southland. One journalist described Nicol as very tall but with a light voice.
After the vote was won, Helen Nicol described herself as 'one who worked harder than any other woman in the South Island for the extension of the franchise to every woman'. She continued to campaign for temperance and was for a time involved with the National Council of Women of New Zealand. Although disappointed that prohibition had not become law, she wrote: 'I have never regretted spending the best years of my life in working to secure the enfranchisement of our New Zealand women, and I do feel that it has bettered the position of the workers'.
Increased domestic responsibilities curtailed Helen Nicol's public life from 1897. She and her sister, Lavinia, reared three nephews, one of whom spoke of Helen as being 'very, very kind.' Helen Nicol had 'no respect for the man or woman who neglects the sacred duties that make home happy'. In later life she welcomed the new opportunities that arose to promote the welfare of women and children. Her mother died in 1904 and Lavinia, who was also engaged in charitable work and writing to the paper, eventually married. Helen Nicol never married; she died in Dunedin on 22 November 1932.