We prove that every weak-local triple derivation on a JB * -triple E (i.e. a linear map T : E → E such that for each φ ∈ E * and each a ∈ E, there exists a triple derivation δ a,φ : E → E, depending on φ and a, such that φT (a) = φδ a,φ (a)) is a (continuous) triple derivation. We also prove that conditions (h1) {a, T (b), c} = 0 for every a, b, c in E with a, c ⊥ b; (h2) P 2 (e)T (a) = −Q(e)T (a) for every norm-one element a in E, and every tripotent e in E * * such that e ≤ s(a) in E * * 2 (e), where s(a) is the support tripotent of a in E * * , are necessary and sufficient to show that a linear map T on a JB * -triple E is a triple derivation.