Leontovych was born and raised in the Podolia province of the Russian Empire (now in Ukraine). He was educated as a priest in the Kamianets-Podilskyi Theological Seminary and later furthered his musical education at the Saint Petersburg Court Capella and private lessons with Boleslav Yavorsky. With the independence of the Ukrainian state in the 1917 revolution, Leontovych moved to Kyiv where he worked at the Kyiv Conservatory and the Mykola Lysenko Institute of Music and Drama.

During his lifetime, Leontovych's compositions and arrangements became popular with professional and amateur groups alike across the Ukrainian region of the Russian Empire. Performances of his works in western Europe and North America earned him the nickname "the Ukrainian Bach" in France. Apart from his very popular Shchedryk, Leontovych's music is performed primarily in Ukraine and the Ukrainian diaspora.
The created Ukrainian Republican Capella has successfully toured Europe and America performing the works of Nikolai Leontovich.

There, he started the city's first music school, since the college where he had worked was closed down by the Bolsheviks. He also began to work on his first major symphonic work, the opera Na Rusalchyn Velykden' (On the water nymph's Great Day).
During the night of 22–23 January 1921, Mykola Leontovych was murdered by Chekist (Soviet state security) agent Afanasy Grishchenko. Leontovych was staying at the home of his parents, whom he was visiting for the Orthodox Feast of the Nativity (25 December in the Julian calendar, which, in the Gregorian calendar, adopted by the USSR only in 1918, falls in January).

On February 1, 1921, a significant group of cultural figures, professors and students gathered at the Kiev Music and Drama Institute named after Nikolai Lysenko to celebrate 9 days after the death of Nikolai Leontovich, according to Christian custom. Quickly, but with great responsibility, they organized a concert of Leontovich's works, spoke with words of regret and sorrow. At this meeting, the Committee in memory of Nikolai Leontovich was created, which later took shape as the Musical Society named after ND Leontovich. This society included such famous Ukrainian artists as Boris Lyatoshinsky and Pavlo Tychina. Today, the name of Leontovich is borne by Ukrainian musical groups, in particular the Bandura Chapel and educational institutions (in particular, the Vinnytsia School of Arts and Culture, Donetsk Music School No. 1, Pokrovsk Music School, Kharkiv School of Arts No. 4).
Streets in Kiev, Odessa, Lvov and other Ukrainian cities are named after Leontovich.
The Leontovich Memorial Museum operates in the city of Tulchin, Vinnitsa region; in 1977, the Leontovich Museum was also opened in the village. Markovka not far from the place of his burial.
In 1977, 37 choral works by Leontovich were recorded by the choir of students of the Kiev Conservatory under the direction of P. Muravsky.
In 2005, a disc with 32 spiritual works of Leontovich was released by the Kiev chamber choir under the direction of N. Gobdych.

Mykola Leontovych was highly critical of himself. According to his first biographer Oles' Chapkivskyi, a contemporary of the composer, Leontovych would sometimes work on one choral setting without letting anyone else see it for up to four years. After the publication of his Second Compilation of Songs from Podolia, he changed his mind and was not fully satisfied with it, and as a result he bought all 300 copies and had them destroyed.
Chapkivskyi also described Leontоvych as having a shy personality, saying "He abstained from fame, feared attention and advertisement." On the other hand, Chapkivskyi claimed that Leontovych's jealousy, fear of competition, and fear of non-acceptance from the established musical society, caused the music of Leontovych to be little known.
Zynoviy Yaropud of the Kamianets-Podilskyi State Pedagogical University writes that "all of [Leontovych's] contemporaries called him a quiet, gentle person.
Leontovych's friend, O. Buzhanskiy, recalls that the composer was "always full of humour; spoke so that everyone was laughing to tears, but he remained serious and stayed calm."
Leontovych had an original style. Many of his works have "deft use of imitative counterpoint and impressionistic harmony." He had a strong desire for his music to arouse the senses, especially sight, saying, "I'm interested in which colours you used for high tones, and which for the low ones. I myself often think about that, to combine sound and colour."
His choral compositions feature rich harmony, vocal polyphony, and imitation. His earlier choral arrangements of folk songs were primarily strophic arrangements of the melody. As the composer gained more experience, the structure of his choral compositions and arrangements of folk songs became more frequently intertwined with text.

Leontovych arranged many Ukrainian folk songs, creating artistically independent choral compositions based on their melodies and lyrics. He followed the traditions of improvisation of Ukrainian kobzars, who would interpret every new strophe differently. He also employed humming and the variability in timbre of singers' voices as techniques in reaching a desired emotional or sensual effect.
A central topic of Leontovych's work is choral music about everyday life. His music frequently reflect actual actions and events. An example of this is his shchedrivka Ой там за горою (Oh there behind the Mountain) in which a tenor initially starts the song with a solo and the rest of the voices of the choir gradually come in, reflecting carolling when new groups of singers join in. Then, a switching of parts begins between different groups of the choir, recreating the clamorous atmosphere of the New Year's Eve.
For most of his career, Leontovych kept his music to himself, only performing it during his own concerts. This was because of the composer's highly self-critical and shy personality. Leontovych's first critic was his friend and fellow priest and composer Kyrylo Stetsenko, who described him to be "a great expert of both choral singing and theoretical studies". He also convinced Leontovych to publish his music and have it performed by the Kyiv University.
The successful debut of "Shchedryk" earnt Leontovych popularity among specialists and fans of choral music in Kyiv.
After reviewing Leontovych's Second Compilation of Songs from Podolia, Lysenko wrote: "Leontovych has an original, illustrious gift. In his arrangements I found separate passages, movement of voices, which later developed in an ingeniously weaved musical network."
Apart from Shchedryk, or the Carol of the Bells, Leontovych's music is currently performed mostly in Ukraine and few recordings are dedicated exclusively to him.