We show that if $$Y_j\subset \mathbb {C}^{n_j}$$
Y
j
⊂
C
n
j
is a bounded strongly convex domain with $$C^3$$
C
3
-boundary for $$j=1,\dots ,q$$
j
=
1
,
⋯
,
q
, and $$X_j\subset \mathbb {C}^{m_j}$$
X
j
⊂
C
m
j
is a bounded convex domain for $$j=1,\ldots ,p$$
j
=
1
,
…
,
p
, then the product domain $$\prod _{j=1}^p X_j\subset \mathbb {C}^m$$
∏
j
=
1
p
X
j
⊂
C
m
cannot be isometrically embedded into $$\prod _{j=1}^q Y_j\subset \mathbb {C}^n$$
∏
j
=
1
q
Y
j
⊂
C
n
under the Kobayashi distance, if $$p>q$$
p
>
q
. This result generalises Poincaré’s theorem which says that there is no biholomorphic map from the polydisc onto the Euclidean ball in $$\mathbb {C}^n$$
C
n
for $$n\ge 2$$
n
≥
2
. The method of proof only relies on the metric geometry of the spaces and will be derived from a more general result for products of proper geodesic metric spaces with the sup-metric. In fact, the main goal of the paper is to establish a general criterion, in terms of certain asymptotic geometric properties of the individual metric spaces, that yields an obstruction for the existence of an isometric embedding between product metric spaces.