We present the first search for the decay B 0 → K 0 S K 0 S K 0 L using a data sample of 232 × 10 6 B ¯¯¯ B pairs. We find no statistically significant evidence for the nonresonant component of this decay. Our central value for the branching fraction, assuming the true Dalitz distribution is uniform and excluding the ϕ resonance, is B ( B 0 → K 0 S K 0 S K 0 L ) = ( 2.4 + 2.7 − 2.5 ± 0.6 ) × 10 − 6 where the errors are statistical and systematic, respectively. We set a single-sided Bayesian upper limit of B ( B 0 → K 0 S K 0 S K 0 L ) < 7.4 × 10 − 6 at 90% confidence level using a uniform prior probability for physical values. Assuming the worst-case true Dalitz distribution, where the signal is entirely in the region of lowest efficiency, the 90% confidence level upper limit is B ( B 0 → K 0 S K 0 S K 0 L ) < 16 × 10 − 6 .