Does departure tax apply to a family trust I'm a beneficiary of when I leave Canada?

It can, but the answer depends on exactly what you hold. Being a discretionary beneficiary of a family trust, someone who might receive a distribution if the trustees decide to make one but has no fixed entitlement, is different from owning a defined capital interest in a trust, and the departure tax rules apply based on what kind of property you actually own, not simply on your connection to the trust. A defined capital interest that qualifies as taxable Canadian property, or certain other defined interests, can be swept into the deemed disposition; a purely discretionary beneficiary interest with no fixed entitlement is treated differently and generally isn't valued and taxed the same way.

Because trust structures vary widely, some beneficiaries hold clearly defined interests, others hold nothing more than a hope of future discretion, this is not a question with a single answer that applies to every family trust arrangement. The trust's own terms, and the specific nature of what you hold under them, need to be reviewed alongside the departure-tax rules before you leave.

If you're a beneficiary of a family trust and planning to emigrate, getting the trust document and your specific interest reviewed as part of your departure planning is a necessary step, not an optional add-on.