Ní Mhaonaigh is recognised as a leading exponent in the Donegal fiddle tradition, and she is often considered one of the foremost singers in the Irish language, her native tongue.

[1] She was part of the Irish supergroup T with the Maggies who performed in January 2009 at Temple Bar TradFest in Dublin their first ever two concerts under that name and who released in October 2010 their debut (and to date only) album.

[2] After nearly 22 years with Altan, on 28 December 2008 Ní Mhaonaigh premiered in Gweedore (during the Frankie Kennedy Winter Music School) her debut solo album Imeall which was later released worldwide in February 2009.

At the time, Kennedy and Ní Mhaonaigh were earning their living by teaching at St. Oliver Plunkett National School in Malahide, north County Dublin.

But live performances in 1984 and 1985, particularly in the United States, convinced them that there was an audience for "no-compromise traditional music played with heart and drive," and they were persuaded to give up teaching.

On 28 December 2008, at the Frankie Kennedy Winter Music School in Gweedore, Ní Mhaonaigh premiered live some songs from the album in an intimate concert with Lunny.

[8][9] Since February 2009, Ní Mhaonaigh (fiddle, lead vocals) has toured solo and (mostly) as a trio with Manus Lunny (bouzouki) & James Higgins (percussions).

Ní Mhaonaigh also contributed a track, Má Théid Tú Chun Aonaigh to the Irish charitable album Ceol Cheann Dubhrann which was released in December 2009 to raise funds for two projects in Ranafast, a Gaeltacht area from which she has collected songs.

[nb 2] Mairéad Ní Mhaonaigh and Friends Full Concert was held as a live stream on Sunday evening 24 January 2021 (at 8pm GMT) (€10 per household) during Letterkenny Trad Week 2021 at the An Grianán Theatre.

[13][14] On 5 March 2021, Ní Mhaonaigh announced that her new music piece "Ré an tSolais" would be broadcast on TG4 as part of a show due to be performed on St Patrick's Day 2021 (at 9:30pm GMT).

[16][nb 7] On 7 January 2016, Ní Mhaonaigh announced on her Facebook page that the new band called Na Mooneys that she had formed (along with her nephew Ciarán Ó Maonaigh and her siblings Anna Ní Mhaonaigh and Gearóid Ó Maonaigh) two years earlier (during the last Frankie Kennedy Winter School[nb 8] where they performed their first ever show)[18] were in the process of recording their debut family album.

[22] On 6 February 2016, the new band Na Mooneys announced that they were just near the end of the recording of their debut album in Manus Lunny's studio, with Anna and Mairéad Ní Mhaonaigh putting down some vocals for a few songs, before to get ready for the mix.

[24] On 9 September 2016, Na Mooneys announced that they are due to perform their Dublin debut show on 29 January 2017 at St. Michan's Church during the Temple Bar TradFest.

[nb 10] On 4 September 2022, it was announced that Ní Mhaonaigh (fiddle / vocals) would do a 9-date autumnal Irish (& UK) concert tour from 14 September to 2 October 2022 with harpist Cormac De Barra (harp / vocals) and piper Mark Redmond (uilleann pipes / flute / whistles) in Dublin, Dún Laoghaire, Tinahely, Baile Mhúirne, Hammersmith (London), Clifden, Belmullet, Newbridge, Cork (€5-€25).