The tone of the poem is didactic. This means that it sets out to teach, to instruct. The speaker is a father advising his son how to live his life, but the lesson can apply to any reader, and indeed the poem continues to find much favour with audiences; undoubtedly it is Kipling’s best known and best loved poem.
The tone of the poem might also be called hortatory, meaning that it urges and encourages the addressee towards following a certain path, as the father aims to inculcate a whole set of morals and values in his son. Kipling employs a colloquial style for the work, and this use of everyday, conversational, easy-to-understand language has contributed to the poem's widespread and lasting appeal.
The mood of the poem is solemn and sober, calling for restraint, balance and fortitude through every aspect of life, even the greatest hardships. If the young man is able to achieve this, then, the father declares emphatically in the closing two lines:
Yours is the Earth and everything that’s in it;
And - which is more - you’ll be a Man, my son!
The poem, then, ends on a positive note, with a picture of ideal manhood, fully attained, and in command of life and the world. However, it is easy to miss the overall conditional tone of the poem; the young man will achieve such success only if he follows the exacting commands laid down in the poem. The ‘if’ of the title looms large; the individual state of resilience, balance and strength envisioned in this poem is by no means easy to achieve.