Literary critics and historians have tended to partition Chaucer's literary career into three major periods: the French, the Italian and the English, of which the last is a development of the first two.
What is referred to as Chaucer's French period lasted until 1372. The poems of the earliest or French group are closely modelled upon French originals. According to Edward Albert the style was clumsy and immature. During this time, Chaucer translated the "Roman de la Rose," a French poem written during the 1200s. It is a lengthy allegorical poem, written in octosyllabic couplets. He also wrote his Book of the Duchess, an elegiac poem that shared much with contemporary French poetry of the time but also departed from that poetry in important ways. Chaucer's extensive reading of Latin poets such as Boethius also influenced his own work.
A journey to Italy in 1372 kicked off what is now widely considered to be Chaucer's Italian period, which lasted from 1372 to 1385. The trip introduced him to the works of contemporary Italian writers, such as Dante, Petrarch and Boccaccio. This stage shows a decided advance upon the first. In the handling of the metres the technical ability is greater, and there is a growing keenness of perception and a greater stretch of originality. To this period belong Anelida and Arcite and The Parlement of Foules. The latter has a fine opening, and, in the characterization of the birds, shows Chaucer's true comic spirit. Troilus and Criseyde is a long love poem that he adapted from Boccaccio's "Il Filostrato.", but in its emphasis on character it is original, and indicative of the line of Chaucer's development. Reality and a passionate intensity underlie its conventions of courtly love and the tedious descriptions which this code demanded. The complex characters of Criseyde and Pan-darus reveal a new subtlety of psychological development, and indicate Chaucer's growing insight into human motives. Troilus and Criseyde is held to be Chaucer's best narrative work. The rhyme royal stanzas are of much dexterity and beauty, and the pathos of the story is touched upon with deep feeling. The House of Fame, a poem in octosyllabic couplets, is of the dream-allegory type. In his dream Chaucer is carried by an eagle to the House of Fame and watches candidates for fame approach the throne, some being granted their requests and others refused. Though the story is rather drawn-out, and the allegorical significance obscure, it is of special interest because, in the verve and raciness of the Eagle, it shows gleams of the genuine Chaucerian humour. In this group is also included The Legend of Good Women, in which Chaucer, starting with the intention of telling nineteen affecting tales of virtuous women of antiquity, finishes with eight accomplished and the ninth only begun. After a charming introduction on the daisy, there is some masterly narrative, particularly in the portion dealing with Cleopatra. The poem is the first known attempt in English to use the heroic couplet, which is, none the less, handled with great skill and freedom.
During the final period of Chaucer's literary career, sometimes referred to as the English period (1385-1400), Chaucer wrote the work for which he is now best known, "The Canterbury Tales." In this classic of English literature, Chaucer tells the stories of a group of disparate travelers on a journey. Often sharp and funny, "The Canterbury Tales" was more innovative and less formulaic than other contemporary English poetry, such as the work of John Gower.
For the general idea of the tales Chaucer may be indebted to Boccaccio, but in nearly every important feature the work is essentially English. For the purposes of his poem Chaucer draws together twenty-nine pilgrims, including himself. They meet at the Tabard Inn, in Southwark in order to go on a pilgrimage to the tomb of Thomas a Becket at Canterbury. The twenty-nine are carefully chosen types, of both sexes, and of all ranks, from a knight to a humble ploughman; their occupations and personal peculiarities are many and diverse; and, as they are depicted in the masterly Prologue to the main work, they are interesting, alive, and thoroughly human. At the suggestion of the host of the Tabard, and to relieve the tedium of the journey, each of the pilgrims is to tell two tales on the outward journey, and two on the return. In its entirety the scheme would have resulted in an immense collection of over a hundred tales. But as it happens Chaucer finished only twenty, and left four partly complete. The separate tales are linked with their individual prologues, and with dialogues and scraps of narrative. Even in its incomplete state the work is a great literature in itself, an almost unmeasured abundance and variety of humour and pathos, of narrative and description, and of dialogue and digression. There are two prose tales, Chaucer's own Tale of Melibeus and The Parson's Tale; and nearly all the others are composed in a powerful and versatile species of the decasyllabic or heroic couplet. To this last stage of Chaucer's work several short poems are ascribed, including The Lak of Stedfastnesse and the serio-comic Compleynte of Chaucer to his Empty Purse. There is also mention of a few short early poems, such as Origines upon the Maudeleyne, which have been lost.
Although the three phases shows the general development of Chaucer’s poetic career, in none of these divisions, of course, is the one influence felt to the exclusion of the others. It is merely that one predominates.