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As a light leaf wash on the smooth-leaved ones, yes. Succulents with broad, flat leaves, such as jade plant, aloe, haworthia and the larger echeverias, sit on sunny windowsills and collect dust like any other houseplant, and a weak neem wash lifts it and gives the leaves back their natural finish. Cacti and the fine-spined succulents are a different matter: there is nothing to wipe, and a wash sits in the spines. Dust those with a soft, dry paintbrush instead.
The powdery bloom
Some succulents, echeveria and dudleya among them, carry a pale, powdery coating on the leaf called farina. It is part of the plant, and once it is rubbed off it does not come back on that leaf. On those, either skip the wash altogether or mist very lightly and leave it to dry without touching the leaves.
Which mix
The light wash only: one part water-soluble neem to a hundred parts of tepid water, or 5 ml of pure neem oil with 1 to 2 ml of liquid soap in a litre of warm water, shaken until milky. The recipe is on our leaf-shine spray page. Succulents do not need the richer mix.
How and when
Morning or evening, out of direct sun, and let the leaves dry fully before the plant goes back to its bright window. Mist lightly, then wipe each leaf with a soft cloth, working from the centre of the rosette outwards so the wash does not pool in the crown. If it does pool, tip the plant gently to let it run out. Do one leaf first on anything you have not washed before and look at it the next day. Once every month or two is plenty; succulents gather dust slowly.
Mix fresh
Make what you will use in one session, use it within 48 hours and tip the rest away. Neem oil sets when it is cool, so warm the bottle in a bowl of warm water before measuring and use warm water in the sprayer. The earthy neem smell fades as the leaves dry.