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Using a 281 pb data sample collected at the ψ(3770) with the CLEO-c detector, we present the first absolute branching fraction measurement of the decay D → Kππeνe at a statistical significance of about 4.0 standard deviations. We find 10 candidates consistent with the decay D → Kππeνe. The probability that a background fluctuation accounts for this signal is less than 4.1 × 10. We find B(D0 → Kππeνe) = [2.8 −1.1(stat) ± 0.3(syst)] × 10. This channel is consistent with being predominantly produced through D → K− 1 (1270) eνe. By restricting the invariant mass of the hadronic system to be consistent with K1(1270), we obtain the product of branching fractions B(D0 → K− 1 (1270) eνe) · B(K 1 (1270) → Kππ) = [2.5 −1.0 (stat) ± 0.2 (syst)] × 10. Using B(K 1 (1270) → Kππ) = (33 ± 3)%, we obtain B(D0 → K− 1 (1270) eνe) = [7.6 −3.0 (stat) ± 0.6 (syst) ± 0.7] × 10. The last error accounts for the uncertainties in the measured K− 1 (1270) → Kππ branching fraction. PACS numbers: 13.20.Fc, 12.38.Qk, 14.40.Lb