Alecsandri was born in the Moldavian town of Bacău, to a family of landowners. His parents were Vasile Alecsandri and Elena Cozoni, and his mother was the daughter of a Greek Romanian merchant. His parents had seven children, of which three survived: one daughter, Catinca, and two sons, Iancu — a future army colonel — and Vasile.

The family prospered in the lucrative business of salt and cereals trade. In 1828, they purchased a large estate in Mirceşti, a village near Siret River. The young Vasile spent time there studying with a devout monk from Maramureş, Gherman Vida, and playing with Vasile Porojan, a Gypsy boy who became a dear friend. Both characters would later appear in his work.

Between 1828 and 1834, he studied at the Victor Cuenim 'pensionnat', an elite boarding school for boys in Iaşi. He moved to Paris in 1834, where he dabbled in chemistry, medicine, and law, but soon abandoned all in favor of what he called his "lifelong passion", literature. He penned his first literary essays in 1838 in French, which he had mastered to perfection during his stay in Paris. After a brief return home, he left for Western Europe again, visiting Italy, Spain, and southern France.

A year later, Alecsandri attended a party celebrating the name day of Costache Negri, a family friend. He there fell in love with Negri's sister. The 21 year old and not long divorced Elena Negri responded enthusiastically to the 24 year old youngster's love declarations. Alecsandri began writing love poems until a sudden illness forced Elena to head abroad to Venice. He met her there, where they shared two torrid months.

They cruised to Austria, Germany, and to Alecsandri's former romping grounds, France. Elana's chest illness aggravated in Paris, and after a brief stint in Italy, they both boarded a French ship to return home 25 April 1847. Tragedy struck on the ship, when Elena died in her lover's arms. Alecsandri channeled his mourning into a poem, "Steluţa" (Little Star). Later, he dedicated his "Lăcrimioare" (Little Tears) collection of poems to her.

In 1848, he became one of the leaders of the revolutionary movement based in Iaşi. He wrote a widely read poem urging the public to join the cause, "Către Români" (To Romanians), later renamed "Deşteptarea României" (Romania's Awakening). Together with Mihail Kogălniceanu and Costache Negri, he wrote a manifesto of the revolutionary movement in Moldavia, "Dorinţele partidei naţionale din Moldova" (Wishes of the National Party of Moldavia).

However, as revolution failed, he fled Moldavia through Transylvania and Austria, moving on to Paris, where he continued to write political poems.

After two years, he returned to a triumphant staging of his new comedy, "Chiriţa în Iaşi". He toured the Moldavian countryside, collecting, reworking, and arranging a vast array of Romanian folklore, which he published in two installments, in 1852 and 1853. The poems included in these two enormously popular collections became the cornerstone of the emerging Romanian identity, especially the ballads "Mioriţa", "Toma Alimoş", "Mânăstirea Argeşului", and "Novac şi Corbul." His volume of original poetry, "Doine şi Lăcrămioare", further cemented his reputation.

Broadly revered in Romanian cultural circles, he oversaw the establishment of "România Literară", to which writers from both Moldavia and Wallachia contributed. He was one of the most vocal unionists, supporting the union the two Romanian provinces, Moldavia and Wallachia. In 1856, he published in Mihail Kogălniceanu's newspaper, Steaua Dunării, the poem "Hora Unirii", which became the anthem of the unification movement.

The end of 1855 saw Alecsandri pursuing a new romantic interest, in spite of promises made to Elena Negri on her deathbed. At age 35, the now renowned poet and public figure fell in love with the young Paulina Lucasievici, the daughter of an innkeeper. The romance moved at a lightning pace: they moved in together to Alecsandri's estate at Mirceşti and, in 1857, their daughter Maria was born.

Alecsandri found satisfaction in the advancement of those political causes he had long championed. The two Romanian provinces united and he was appointed minister of External Affairs by Alexandru Ioan Cuza. He toured the West, pleading to some of his friends and acquaintances in Paris to acknowledge the newly formed nation and support its emergence in the turbulent Balkan area.

The diplomatic tours tired him. In 1860, he settled in Mirceşti for what would be the rest of his life. He married Paulina more than a decade and a half later, in 1876.

Between 1862 and 1875, Alecsandri wrote 40 lyrical poems, including "Miezul Iernii, "Serile la Mirceşti, "Iarna," "La Gura Sobei", "Oaspeţii Primăverii", and "Malul Siretului." He also dabbled in epic poems, collected in the volume "Legende" , and he dedicated a series of poems to the soldiers who participated in the Romanian War of Independence.

In 1879, his "Despot-Vodă" drama received the award of the Romanian Academy. He continued to be a prolific writer, finishing a fantastic comedy, "Sânziana şi Pepelea," (1881) and two dramas, "Fântâna Blanduziei" (1883) and "Ovidiu" (1884).

In 1881, he wrote Trăiască Regele (Long Live the King), which became the national anthem of the Kingdom of Romania until the abolition of monarchy in 1947.

Long suffering from cancer, Alecsandri died in 1890 at his estate in Mirceşti.