In its final form, the work has six movements, grouped into two Parts:
  1. Kräftig. Entschieden (Strong and decisive) [D minor to F major]
  2. Tempo di Menuetto (In the tempo of a minuet) [A major]
  3. Comodo (Scherzando) (Comfortably, like a scherzo) [C minor to C major]
  4. Sehr langsam—Misterioso (Very slowly, mysteriously) [A minor]
  5. Lustig im Tempo und keck im Ausdruck (Cheerful in tempo and cheeky in expression) [F major]
  6. Langsam—Ruhevoll—Empfunden (Slowly, tranquil, deeply felt) [D major]
The first movement alone, with a normal duration of a little more than thirty minutes, sometimes forty, forms Part One of the symphony. Part Two consists of the other five movements and has a duration of about sixty to seventy minutes.
As with each of his first four symphonies, Mahler originally provided a programme of sorts to explain the narrative of the piece. He did not reveal the structure and content to the public. But, at different times, he shared evolving versions of a program for the third symphony with various friends, including: Max Marschalk, a music critic; violist Natalie Bauer-Lechner, a close friend and confidante; and Anna von Mildenburg, the dramatic soprano and Mahler's lover during the summer of 1896 when he was completing the symphony. Bauer-Lechner wrote in her private journal that Mahler said, "You can't imagine how it will sound!"
In its simplest form, the program consists of a title for each of the six movements:
  1. "Pan Awakes, Summer Marches In"
  2. "What the Flowers in the Meadow Tell Me"
  3. "What the Animals in the Forest Tell Me"
  4. "What Man Tells Me"
  5. "What the Angels Tell Me"
  6. "What Love Tells Me"
Mahler, however, elaborated on this basic scheme in various letters. In an 1896 letter to Max Marschalk, he called the whole "A Summer's Midday Dream," and within Part One, distinguished two sections, "Introduction: Pan awakes" and "I. Summer marches in (Bacchic procession)". In a June 1896 letter to Anna von Mildenburg, Mahler reaffirmed that he conceived the first movement in two sections: I. What the stony mountains tell me; II. Summer marches in. In another letter to Mildenburg from Summer 1896, he said that "Pan" seemed to him the best overall title (Gesamttitel) for the symphony, emphasizing that he was intrigued by Pan's two meanings, a Greek god and a Greek word meaning "all."
All these titles were dropped before publication in 1898.
Mahler originally envisioned a seventh movement, "Heavenly Life" (alternatively, "What the Child Tells Me"), but he eventually dropped this, using it instead as the last movement of the Symphony No. 4. Indeed, several musical motifs taken from "Heavenly Life" appear in the fifth (choral) movement of the Third Symphony.
The symphony, particularly due to the extensive number of movements and their marked differences in character and construction, is a unique work. The opening movement, colossal in its conception (much like the symphony itself), roughly takes the shape of sonata form, insofar as there is an alternating presentation of two theme groups; however, the themes are varied and developed with each presentation, and the typical harmonic logic of the sonata form movement—particularly the tonic statement of second theme group material in the recapitulation—is changed. The symphony starts with a modified theme from the fourth movement of Brahms' first symphony with the same rhythm, but many of the notes are changed. The opening gathers itself slowly into a rousing orchestral march. A solo tenor trombone passage states a bold (secondary) melody that is developed and transformed in its recurrences. At the apparent conclusion of the development, several solo snare drums "in a high gallery" play a rhythmic passage lasting about thirty seconds and the opening passage by eight horns is repeated almost exactly.
As described above, Mahler dedicated the second movement to "the flowers on the meadow". In contrast to the violent forces of the first movement, it starts as a graceful Menuet, but also features stormier episodes.
The third movement, a scherzo, with alternating sections in 2/4 and 6/8 metre, quotes extensively from Mahler's early song "Ablösung im Sommer" (Relief in Summer). In the trio section, a complete mood changes from playful to contemplative occurs with an off-stage post horn (or flugelhorn) solo. The reprise of the scherzo music is unusual, as it is interrupted several times by the post-horn melody.
At this point, in the sparsely instrumentated fourth movement, we hear an alto solo singing a setting of Friedrich Nietzsche's "Midnight Song" from Also sprach Zarathustra ("O Mensch! Gib acht!" ("O man! Take heed!")), with thematic material from the first movement woven into it.
The cheerful fifth movement, "Es sungen drei Engel", is one of Mahler's Des Knaben Wunderhorn songs, (whose text itself is loosely based on a 17th-century church hymn, which Paul Hindemith later used in its original form in his) about the redemption of sins and comfort in belief. Here, a children's choir imitating bells and a female chorus join the alto solo.
Of the great finale, Bruno Walter wrote, “In the last movement, words are stilled—for what language
can utter heavenly love more powerfully and forcefully than music itself? The Adagio, with its broad, solemn
melodic line, is, as a whole—and despite passages of burning pain—eloquent of comfort and grace. It is a
single sound of heartfelt and exalted feelings, in which the whole giant structure finds its culmination.”
The movement begins very softly with a broad D-major chorale melody, which slowly builds to a loud and majestic conclusion culminating on repeated D major chords with bold statements on the timpani.